WorldWideScience

Sample records for colloidal based conducting

  1. Towards conducting inks: Polypyrrole–silver colloids

    International Nuclear Information System (INIS)

    Omastová, Mária; Bober, Patrycja; Morávková, Zuzana; Peřinka, Nikola; Kaplanová, Marie; Syrový, Tomáš; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    2014-01-01

    Graphical abstract: - Highlights: • Composite colloidal particles combining conducting polymer and metal have been prepared. • Conducting colloids are suitable for printing applications. • Polypyrrole/silver colloids are prepared in a single reaction step. • The conductivity control is discussed and still needs improvement. - Abstract: The oxidation of pyrrole with silver nitrate in the presence of suitable water-soluble polymers yields composite polypyrrole–silver colloids. The polypyrrole–silver nanoparticles stabilized with poly(N-vinylpyrrolidone) have a typical size around 350 nm and polydispersity index 0.20, i.e. a moderate polydispersity in size. Similar results have been obtained with poly(vinyl alcohol) as stabilizer. The effect of stabilizer concentration on the particle size is marginal. In the present study, several types of stabilizers have been tested in addition to currently used poly(N-vinylpyrrolidone). Transmission electron microscopy and optical microscopy revealed the gemini morphology of polypyrrole and silver colloidal nanoparticles and confirmed their size and size-distribution determined by dynamic light scattering. The use of colloidal dispersions provides an efficient tool for the UV–vis and FT Raman spectroscopic characterization of polypyrrole, including the transition between polypyrrole salt and corresponding polypyrrole base. The dispersions were used for the preparation of coatings on polyethylene terephthalate foils, and the properties for polypyrrole–silver composites have been compared with those produced from polypyrrole colloids alone

  2. Conductivity maximum in a charged colloidal suspension

    Energy Technology Data Exchange (ETDEWEB)

    Bastea, S

    2009-01-27

    Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.

  3. Towards conducting inks: polypyrrole-silver colloids

    Czech Academy of Sciences Publication Activity Database

    Omastová, M.; Bober, Patrycja; Morávková, Zuzana; Peřinka, N.; Kaplanová, M.; Syrový, T.; Hromádková, Jiřina; Trchová, Miroslava; Stejskal, Jaroslav

    2014-01-01

    Roč. 122, 10 March (2014), s. 296-302 ISSN 0013-4686 R&D Projects: GA TA ČR TE01020022; GA ČR(CZ) GA13-00270S Institutional support: RVO:61389013 Keywords : conducting inks * polypyrrole * colloids Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 4.504, year: 2014

  4. Anomalous electrical conductivity of nanoscale colloidal suspensions.

    Science.gov (United States)

    Chakraborty, Suman; Padhy, Sourav

    2008-10-28

    The electrical conductivity of colloidal suspensions containing nanoscale conducting particles is nontrivially related to the particle volume fraction and the electrical double layer thickness. Classical electrochemical models, however, tend to grossly overpredict the pertinent effective electrical conductivity values, as compared to those obtained under experimental conditions. We attempt to address this discrepancy by appealing to the complex interconnection between the aggregation kinetics of the nanoscale particles and the electrodynamics within the double layer. In particular, we model the consequent alterations in the effective electrophoretic mobility values of the suspension by addressing the fundamentals of agglomeration-deagglomeration mechanisms through the pertinent variations in the effective particulate dimensions, solid fractions, as well as the equivalent suspension viscosity. The consequent alterations in the electrical conductivity values provide a substantially improved prediction of the corresponding experimental findings and explain the apparent anomalous behavior predicted by the classical theoretical postulates.

  5. Colloidal transparent conducting oxide nanocrystals: A new infrared ...

    Indian Academy of Sciences (India)

    2015-06-02

    Jun 2, 2015 ... Home; Journals; Pramana – Journal of Physics; Volume 84; Issue 6. Colloidal transparent conducting oxide nanocrystals: A new infrared plasmonic material. Bharat Tandon ... Angshuman Nag1. Department of Chemistry, Indian Institute of Science Education and Research (IISER), Pune 411 008, India ...

  6. Magnetoresponsive conductive colloidal suspensions with magnetized carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Abdalla, Ahmed M. [Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Abdel Fattah, Abdel Rahman [Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Ghosh, Suvojit [Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Puri, Ishwar K., E-mail: ikpuri@mcmaster.ca [Department of Engineering Physics, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada); Department of Mechanical Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4L7 (Canada)

    2017-01-01

    We synthesize a novel and hitherto unreported class of colloidal suspensions for which the dispersed phase, which consists of multiwall carbon nanotubes (MWNTs) decorated with magnetic nanoparticles (MNPs), is both magnetoresponsive and electrically conductive. Synthesis of the dispersed phase merges processes for producing ferrofluids and magnetic MWNTs (mMWNTs). We explore means to tune the properties of these magnetic conductive colloids (MCCs) by varying the (1) MNP material composition, and (2) MNP:MWNT (w/w) magnetization weight ratio (γ). The mMWNTs are examined using XRD, TEM, EDX and SQUID and MCCs are by measuring their zeta potential and electric conductivity. Magnetite (Fe{sub 3}O{sub 4}) MNPs, which possess a high Curie temperature, produce mMWNTs with high saturation magnetization that respond relatively weakly to temperature variations. Mn{sub 0.2}Cu{sub 0.2}Zn{sub 0.6}Fe{sub 2}O{sub 4} and Cu{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} MNPs with lower Curie temperatures are more sensitive to changing temperature. Increasing the MNP Cu content improves the electric conductivity of the corresponding MCC while increasing γ enhances its magnetic response. After γ is raised above a threshold value, mMWNT decoration on the CNT surface becomes nonuniform since the MNPs now agglomerate perpendicular to the nanotube surface. These colloidal suspensions are a promising new class of material that can be manipulated with a magnetic field to tune their electrical conductivity. - Highlights: ●We synthesize a novel and hitherto unreported class of colloidal suspensions. ●These colloidal suspensions are both magnetoresponsive and electrically conductive. ●The dispersed phase consists of MWNTs decorated with different magnetic nanoparticles. ●These colloids have enhanced magnetic response and electric conductivity (up to 169.5 mS cm{sup −1}). ●It is a promising new class of material that can be manipulated with a magnetic field.

  7. Colloidal Gelation-2 and Colloidal Disorder-Order Transition-2 Investigations Conducted on STS-95

    Science.gov (United States)

    Hoffmann, Monica T.

    2000-01-01

    The Colloidal Gelation-2 (CGEL 2) and Colloidal Disorder-Order Transition-2 (CDOT 2) investigations flew on Space Shuttle Discovery mission STS-95 (also known as the John Glenn Mission). These investigations were part of a series of colloid experiments designed to help scientists answer fundamental science questions and reduce the trial and error involved in developing new and better materials. Industries dealing with semiconductors, electro-optics, ceramics, and composites are just a few that may benefit from this knowledge. The goal of the CGEL 2 investigation was to study the fundamental properties of colloids to help scientists better understand their nature and make them more useful for technology. Colloids consist of very small (submicron) particles suspended in a fluid. They play a critical role in the technology of this country, finding uses in materials ranging from paints and coatings to drugs, cosmetics, food, and drink. Although these products are routinely produced and used, there are still many aspects of their behavior about which scientists know little. Understanding their structures may allow scientists to manipulate the physical properties of colloids (a process called "colloidal engineering") to produce new materials and products. Colloid research may even improve the processing of known products to enhance their desirable properties.

  8. Colloids of polypyrrole nanotubes/nanorods: a promising conducting ink

    Czech Academy of Sciences Publication Activity Database

    Li, Yu; Bober, Patrycja; Apaydin, D. H.; Syrový, T.; Sariciftci, N. S.; Hromádková, Jiřina; Sapurina, Irina; Trchová, Miroslava; Stejskal, Jaroslav

    2016-01-01

    Roč. 221, November (2016), s. 67-74 ISSN 0379-6779 R&D Projects: GA ČR(CZ) GP14-05568P; GA TA ČR(CZ) TE01020022; GA MŠk(CZ) LH14199; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : colloids * polypyrrole * nanotubes Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.435, year: 2016

  9. An agglomeration-based model for colloid filtration.

    Science.gov (United States)

    Chatterjee, Jaideep; Gupta, Santosh Kumar

    2009-05-15

    This paper develops a model for colloid filtration which accounts for the possibility of aggregation of the colloidal particles in the aqueous phase. Depth-wise variation of liquid-phase colloid concentration, C(x), is measured experimentally in the presence of monovalent cations at different concentrations and divalent cations, which confirm that log of C(x) deviates significantly from linearity for all of the above cases. It is also observed that in all systems showing significant removal, preaggregation of the colloids is observed, which confirms the correlation between aggregation of colloids with their retention in saturated porous media, which has been reported earlier. A new model for depth filtration which is based on material balances of the different sized aggregates, which could be present in the colloidal dispersion, is developed. This resulting model, based on differential deposition rates for different sized aggregates, shows good match with the experimentally observed variation of C(x) with depth, for all of the above conditions. A method for estimating model parameters from data is developed. This model remains independent of the actual deposition mechanism, which could be secondary minima attachment of these colloidal aggregates or the entrapment of these colloidal aggregates in regions of confined geometry. This model can be extended to predict the transport of colloids in groundwater.

  10. Colloid electrochemistry of conducting polymer: towards potential-induced in-situ drug release

    International Nuclear Information System (INIS)

    Sankoh, Supannee; Vagin, Mikhail Yu.; Sekretaryova, Alina N.; Thavarungkul, Panote; Kanatharana, Proespichaya; Mak, Wing Cheung

    2017-01-01

    Highlights: • Pulsed electrode potential induced an in-situ drug release from dispersion of conducting polymer microcapsules. • Fast detection of the released drug within the colloid microenvironment. • Improved the efficiency of localized drug release at the electrode interface. - Abstract: Over the past decades, controlled drug delivery system remains as one of the most important area in medicine for various diseases. We have developed a new electrochemically controlled drug release system by combining colloid electrochemistry and electro-responsive microcapsules. The pulsed electrode potential modulation led to the appearance of two processes available for the time-resolved registration in colloid microenvironment: change of the electronic charge of microparticles (from 0.5 ms to 0.1 s) followed by the drug release associated with ionic equilibration (1–10 s). The dynamic electrochemical measurements allow the distinction of drug release associated with ionic relaxation and the change of electronic charge of conducting polymer colloid microparticles. The amount of released drug (methylene blue) could be controlled by modulating the applied potential. Our study demonstrated a surface-potential driven controlled drug release of dispersion of conducting polymer carrier at the electrode interfaces, while the bulk colloids dispersion away from the electrode remains as a reservoir to improve the efficiency of localized drug release. The developed new methodology creates a model platform for the investigations of surface potential-induced in-situ electrochemical drug release mechanism.

  11. Study of the solution thermal conductivity effect on nonlinear refraction of colloidal gold nanoparticles

    Science.gov (United States)

    Sarkhosh, L.; Mansour, N.

    2015-06-01

    In nanoparticle colloidal systems, the thermal nonlinearity is affected by the thermal parameters of the surrounding solution. Having a low temperature gradient rate solution may be a key factor in producing high thermal nonlinear properties in colloids. In this manuscript, the effect of the thermal conductivity of the surrounding liquid environment on the thermal nonlinear refraction of gold nanoparticles (AuNPs) synthesized by laser ablation of a gold target in different solutions is investigated. Gold nanoparticles colloids have been fabricated by the nanosecond pulsed laser ablation of a pure gold plate in different liquid environments with a thermal conductivity range of 0.14-0.60 W mK-1 including cyclohexanone, castor oil, dimethyl sulfoxide, ethylene glycol, glycerin and water. The AuNPs colloids exhibit a UV-Vis absorption spectrum with a surface plasmon absorption peak at about 540  ±  20 nm. The thermal nonlinear optical responses of the gold colloids are measured using the Z-scan technique under low power CW laser irradiation at 532 nm near the surface plasmon peak of the nanoparticles. Our results show that the nonlinear refractive index of the nanoparticle colloids is considerably affected by the thermal conductivity of liquid medium. The largest nonlinear refractive index of -3.1  ×  10-7 cm2 W-1 is obtained for AuNP in cyclohexanone with the lowest thermal conductivity of 0.14 W mK-1 whereas the lowest one of -0.1  ×  10-7 cm2 W-1 is obtained for AuNP in water with the highest thermal conductivity of 0.60 W mK-1. This study shows that the nonlinear refractive index value of colloids can be controlled by the thermal conductivity of the used liquid’s environment. This allows us to design low threshold optical limiters by choosing a solution with low thermal conductivity for colloidal nanoparticles.

  12. Cell-compatible conducting polyaniline films prepared in colloidal dispersion mode

    Czech Academy of Sciences Publication Activity Database

    Kašpárková, V.; Humpolíček, P.; Capáková, Z.; Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Rejmontová, P.; Junkar, I.; Lehocký, M.; Mozetič, M.

    2017-01-01

    Roč. 157, 1 September (2017), s. 309-316 ISSN 0927-7765 R&D Projects: GA ČR(CZ) GA17-05095S Institutional support: RVO:61389013 Keywords : polyaniline * conducting films * colloidal dispersions Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 3.887, year: 2016

  13. Bead-Based Microfluidic Sediment Analogues: Fabrication and Colloid Transport.

    Science.gov (United States)

    Guo, Yang; Huang, Jingwei; Xiao, Feng; Yin, Xiaolong; Chun, Jaehun; Um, Wooyong; Neeves, Keith B; Wu, Ning

    2016-09-13

    Mobile colloids can act as carriers for low-solubility contaminants in the environment. However, the dominant mechanism for this colloid-facilitated transport of chemicals is unclear. Therefore, we developed a bead-based microfluidic platform of sediment analogues and measured both single and population transport of model colloids. The porous medium is assembled through a bead-by-bead injection method. This approach has the versatility to build both electrostatically homogeneous and heterogeneous media at the pore scale. A T-junction at the exit also allowed for encapsulation and enumeration of colloids effluent at single particle resolution to give population dynamics. Tortuosity calculated from pore-scale trajectory analysis and its comparison with lattice Boltzmann simulations revealed that transport of colloids was influenced by the size exclusion effect. The porous media packed by positively and negatively charged beads into two layers showed distinctive colloidal particle retention and significant remobilization and re-adsorption of particles during water flushing. We demonstrated the potential of our method to fabricate porous media with surface heterogeneities at the pore scale. With both single and population dynamics measurement, our platform has the potential to connect pore-scale and macroscale colloid transport on a lab scale and to quantify the impact of grain surface heterogeneities that are natural in the subsurface environment.

  14. The colloid investigations conducted at the Aespoe Hard Rock Laboratory during 2000-2004

    Energy Technology Data Exchange (ETDEWEB)

    Laaksoharju, Marcus [Geopoint AB, Stockholm (Sweden); Wold, Susanna [Royal Inst. of Tech., Stockholm (Sweden). School of Chemical Science and Engineering, Nuclear Chemistry] (eds.)

    2005-12-15

    In 2000, SKB decided to initiate an international colloid project at the Aespoe Hard Rock Laboratory in Sweden. The objectives of the colloid project are to: (i) study the role of bentonite as a colloid source, (ii) verify the background colloid concentration at Aespoe HRL and, (iii) investigate the potential for colloid formation/transport in natural groundwater concentrations. The experimental concepts for the colloid project are: laboratory experiments with bentonite, background field measurements of natural colloids, borehole specific bentonite colloid stability experiments and a fracture specific transport experiment. The activities concerning the laboratory experiments and background field measurements are described in this work; the other activities are ongoing or planned. The following conclusions were made: The bentonite colloid stability is strongly dependent on the groundwater ionic strength. Natural colloids are organic degradation products such as humic and fulvic acids, inorganic colloids (clay, calcite, iron hydroxide) and microbes. Microbes form few but large particles and their concentration increase with increasing organic carbon concentrations. The small organic colloids are present in very low concentrations in deep granitic groundwater. The concentrations can be rather high in shallow waters. The colloid concentration decreases with depth and salinity, since colloids are less stable in saline waters. The colloid content at Aespoe is less than 300 ppb. The colloid content at repository level is less than 50 ppb. The groundwater variability obtained in the boreholes reflects well the natural groundwater variability along the whole HRL tunnel.

  15. Bright infrared LEDs based on colloidal quantum-dots

    KAUST Repository

    Sun, Liangfeng

    2013-01-01

    Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm. © 2013 Materials Research Society.

  16. Analysis on laser plasma emission for characterization of colloids by video-based computer program

    Science.gov (United States)

    Putri, Kirana Yuniati; Lumbantoruan, Hendra Damos; Isnaeni

    2016-02-01

    Laser-induced breakdown detection (LIBD) is a sensitive technique for characterization of colloids with small size and low concentration. There are two types of detection, optical and acoustic. Optical LIBD employs CCD camera to capture the plasma emission and uses the information to quantify the colloids. This technique requires sophisticated technology which is often pricey. In order to build a simple, home-made LIBD system, a dedicated computer program based on MATLAB™ for analyzing laser plasma emission was developed. The analysis was conducted by counting the number of plasma emissions (breakdowns) during a certain period of time. Breakdown probability provided information on colloid size and concentration. Validation experiment showed that the computer program performed well on analyzing the plasma emissions. Optical LIBD has A graphical user interface (GUI) was also developed to make the program more user-friendly.

  17. Using Android-Based Educational Game for Learning Colloid Material

    Science.gov (United States)

    Sari, S.; Anjani, R.; Farida, I.; Ramdhani, M. A.

    2017-09-01

    This research is based on the importance of the development of student’s chemical literacy on Colloid material using Android-based educational game media. Educational game products are developed through research and development design. In the analysis phase, material analysis is performed to generate concept maps, determine chemical literacy indicators, game strategies and set game paths. In the design phase, product packaging is carried out, then validation and feasibility test are performed. Research produces educational game based on Android that has the characteristics that is: Colloid material presented in 12 levels of game in the form of questions and challenges, presents visualization of discourse, images and animation contextually to develop the process of thinking and attitude. Based on the analysis of validation and trial results, the product is considered feasible to use.

  18. Conducting Polymer Based Nanobiosensors

    Directory of Open Access Journals (Sweden)

    Chul Soon Park

    2016-06-01

    Full Text Available In recent years, conducting polymer (CP nanomaterials have been used in a variety of fields, such as in energy, environmental, and biomedical applications, owing to their outstanding chemical and physical properties compared to conventional metal materials. In particular, nanobiosensors based on CP nanomaterials exhibit excellent performance sensing target molecules. The performance of CP nanobiosensors varies based on their size, shape, conductivity, and morphology, among other characteristics. Therefore, in this review, we provide an overview of the techniques commonly used to fabricate novel CP nanomaterials and their biosensor applications, including aptasensors, field-effect transistor (FET biosensors, human sense mimicking biosensors, and immunoassays. We also discuss prospects for state-of-the-art nanobiosensors using CP nanomaterials by focusing on strategies to overcome the current limitations.

  19. Electrically induced interactions between colloidal particles in the vicinity of a conducting plane

    Science.gov (United States)

    Nadal, François; Argoul, Françoise; Hanusse, Patrick; Pouligny, Bernard; Ajdari, Armand

    2002-06-01

    We address the problem of two-dimensional (2D) colloidal aggregation driven by an ac electrical field, by observing an aqueous dispersion of latex microspheres in contact with a conducting surface. Using micron-sized carboxylated polystyrene particles, we have systematically investigated the aggregation process, as a function of particle size and charge, and of the applied electric field amplitude and frequency. A low-density 2D phase is observed at high frequency (typically above 1 kHz), while at low frequency (below a ``contact frequency'' νc) the collection of particles collapses into disconnected compact aggregates of crystalline (hexagonal) structure. We argue that this scenario is governed by the competition between an attractive force, of electrohydrodynamic nature, and a repulsive force, basically an electrical dipole-dipole interaction. Both contributions are revealed and analyzed in independent experiments on isolated particle pairs, using optical manipulation and dynamometry.

  20. Cell-compatible conducting polyaniline films prepared in colloidal dispersion mode.

    Science.gov (United States)

    Kašpárková, Věra; Humpolíček, Petr; Capáková, Zdenka; Bober, Patrycja; Stejskal, Jaroslav; Trchová, Miroslava; Rejmontová, Petra; Junkar, Ita; Lehocký, Marián; Mozetič, Miran

    2017-09-01

    Conducting polyaniline can be prepared and modified using several procedures, all of which can significantly influence its applicability in different fields of biomedicine or biotechnology. The modifications of surface properties are crucial with respect to the possible applications of this polymer in tissue engineering or as biosensors. Innovative technique for preparing polyaniline films via in-situ polymerization in colloidal dispersion mode using four stabilizers (poly-N-vinylpyrrolidone; sodium dodecylsulfate; Tween 20 and Pluronic F108) was developed. The surface energy, conductivity, spectroscopic features, and cell compatibility of thin polyaniline films were determined using contact-angle measurement, the van der Pauw method, Fourier-transform infrared spectroscopy, and assay conducted on mouse fibroblasts, respectively. The stabilizers significantly influenced not only the surface and electrical properties of the films but also their cell compatibility. Sodium dodecylsulfate seems preferentially to combine both the high conductivity and good cell compatibility. Moreover, the films with sodium dodecylsulfate were non-irritant for skin, which was confirmed by their in-vitro exposure to the 3D-reconstructed human tissue model. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Novel multifunctional colloidal carbohydrate nanofiber electrolytes with excellent conductivity and responses to bone cancer cells.

    Science.gov (United States)

    Gökmen, Fatma Özge; Rzayev, Zakir M O; Salimi, Kouroush; Bunyatova, Ulviya; Acar, Selim; Salamov, Bahtiyar; Türk, Mustafa

    2015-11-20

    This work presents a new approach to fabricating novel polymer nanofiber composites (NFCs) from water solution blends of PVA (hydrolyzed 89%)/ODA-MMT and Na-CMC/ODA-MMT nanocomposites as well as their folic acid (FA) incorporated modifications (NC-3-FA and NC-4-FA) through green electrospinning nanotechnology. The chemical and physical structures and surface morphology of the nanofiber composites were confirmed. Significant improvements in nanofiber morphology and size distribution of the NFC-3-FA and NFC-4-FA nanofibers with lower average means 110 and 113nm compared with those of NFC-1/NFC-2 nanofibers (270 and 323nm) were observed. The structural elements of polymer NFCs, particularly loaded partner NC-2, plays an important role in chemical and physical interfacial interactions, phase separation processing and enables the formation of nanofibers with unique morphology and excellent conductivity (NFC-3-FA 3.25×10(-9)S/cm and NFC-4-FA 8.33×10(-4)S/cm). This is attributed to the higher surface contact areas and multifunctional self-assembled supramacromolecular nanostructures of amorphous colloidal electrolytes. The anticancer activity of FA-containing nanofibers against osteocarcinoma cells were evaluated by cytotoxicity, apoptotic and necrotic analysis methods. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Colloidal gold probe based rapid immunochromatographic strip assay for cortisol

    Energy Technology Data Exchange (ETDEWEB)

    Nara, Seema, E-mail: seemanara@mnnit.ac.in [Department of Applied Mechanics (Biotechnology), Motilal Nehru National Institute of Technology, Allahabad 211004 (India); Department of Reproductive Biomedicine, National Institute of Health and Family Welfare, Munirka, New Delhi 110067 (India); Center for BioMedical Engineering, Indian Institute of Technology, New Delhi 110016 (India); Tripathi, Vinay [Department of Reproductive Biomedicine, National Institute of Health and Family Welfare, Munirka, New Delhi 110067 (India); Center for BioMedical Engineering, Indian Institute of Technology, New Delhi 110016 (India); Singh, Harpal [Center for BioMedical Engineering, Indian Institute of Technology, New Delhi 110016 (India); Shrivastav, Tulsidas G. [Department of Reproductive Biomedicine, National Institute of Health and Family Welfare, Munirka, New Delhi 110067 (India)

    2010-12-03

    A rapid and semi-quantitative immunochromatographic strip (ICS) test for cortisol analysis in serum was developed. The test strip was based on a competitive assay format. Colloidal gold nanoparticles were synthesized and coupled with cortisol-3-carboxymethyloxime-adipic acid dihydrazide-bovine serum albumin (F-3-CMO-ADH-BSA) antigen to directly compete with cortisol in human serum samples. F-3-CMO-ADH-BSA-gold label and uncoupled colloidal gold nanoparticles were appropriately characterized using UV-vis spectroscopy, transmission electron microscopy and atomic force microscopy. Anticortisol antibody raised against F-3-CMO-BSA immunogen in New Zealand white rabbits was coated on the NC membrane as test line. Anti-BSA antibody was used as control line. The lower detection limit of the ICS test was 30 ng mL{sup -1} with visual detection and was completed in 10 min. About 30 human serum samples were also analyzed by the developed strip test and their range of cortisol concentration was established. The developed ICS test is rapid, economic and user friendly.

  3. Stabilising emulsion-based colloidal structures with mixed food ingredients.

    Science.gov (United States)

    Dickinson, Eric

    2013-03-15

    The physical scientist views food as a complex form of soft matter. The complexity has its origin in the numerous ingredients that are typically mixed together and the subtle variations in microstructure and texture induced by thermal and mechanical processing. The colloid science approach to food product formulation is based on the assumption that the major product attributes such as appearance, rheology and physical stability are determined by the spatial distribution and interactions of a small number of generic structural entities (biopolymers, particles, droplets, bubbles, crystals) organised in various kinds of structural arrangements (layers, complexes, aggregates, networks). This review describes some recent advances in this field with reference to three discrete classes of dispersed systems: particle-stabilised emulsions, emulsion gels and aerated emulsions. Particular attention is directed towards explaining the crucial role of the macromolecular ingredients (proteins and polysaccharides) in controlling the formation and stabilisation of the colloidal structures. The ultimate objective of this research is to provide the basic physicochemical insight required for the reliable manufacture of novel structured foods with an appealing taste and texture, whilst incorporating a more healthy set of ingredients than those found in many existing traditional products. © 2012 Society of Chemical Industry.

  4. Electron transport in gold colloidal nanoparticle-based strain gauges

    Science.gov (United States)

    Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M.; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen, Ke; Viau, Guillaume; Ressier, Laurence

    2013-03-01

    A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy EC. This reveals that the Au@CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au@BSPP, Au@TDSP, Au@MPA and Au@MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the EC values of these 14 nm NPs cannot be neglected in determining the β values.

  5. Electron transport in gold colloidal nanoparticle-based strain gauges

    International Nuclear Information System (INIS)

    Moreira, Helena; Grisolia, Jérémie; Sangeetha, Neralagatta M; Decorde, Nicolas; Farcau, Cosmin; Viallet, Benoit; Chen Ke; Viau, Guillaume; Ressier, Laurence

    2013-01-01

    A systematic approach for understanding the electron transport mechanisms in resistive strain gauges based on assemblies of gold colloidal nanoparticles (NPs) protected by organic ligands is described. The strain gauges were fabricated from parallel micrometer wide wires made of 14 nm gold (Au) colloidal NPs on polyethylene terephthalate substrates, elaborated by convective self-assembly. Electron transport in such devices occurs by inter-particle electron tunneling through the tunnel barrier imposed by the organic ligands protecting the NPs. This tunnel barrier was varied by changing the nature of organic ligands coating the nanoparticles: citrate (CIT), phosphines (BSPP, TDSP) and thiols (MPA, MUDA). Electro-mechanical tests indicate that only the gold NPs protected by phosphine and thiol ligands yield high gauge sensitivity. Temperature-dependent resistance measurements are explained using the ‘regular island array model’ that extracts transport parameters, i.e., the tunneling decay constant β and the Coulomb charging energy E C . This reveals that the Au-CIT nanoparticle assemblies exhibit a behavior characteristic of a strong-coupling regime, whereas those of Au-BSPP, Au-TDSP, Au-MPA and Au-MUDA nanoparticles manifest a weak-coupling regime. A comparison of the parameters extracted from the two methods indicates that the most sensitive gauges in the weak-coupling regime feature the highest β. Moreover, the E C values of these 14 nm NPs cannot be neglected in determining the β values. (paper)

  6. Photonic Crystal Fibre SERS Sensors Based on Silver Nanoparticle Colloid

    International Nuclear Information System (INIS)

    Zhi-Guo, Xie; Yong-Hua, Lu; Pei, Wang; Kai-Qun, Lin; Jie, Yan; Hai, Ming

    2008-01-01

    A photonic crystal fibre (PCF) surface enhanced Raman scattering (SERS) sensor is developed based on silver nanoparticle colloid. Analyte solution and silver nanoparticles are injected into the air holes of PCF by a simple modified syringe to overcome mass-transport constraints, allowing more silver nanoparticles involved in SERS activity. This sensor offers significant benefit over the conventional SERS sensor with high flexibility, easy manufacture. We demonstrate the detection of 4-mercaptobenzoic acid (4-MBA) molecules with the injecting way and the common dipping measurement. The injecting way shows obviously better results than the dipping one. Theoretical analysis indicates that this PCF SERS substrate offers enhancement of about 7 orders of magnitude in SERS active area

  7. An electrochemical metalloimmunoassay based on a colloidal gold label.

    Science.gov (United States)

    Dequaire, M; Degrand, C; Limoges, B

    2000-11-15

    A novel, sensitive electrochemical immunoassay has been developed using a colloidal gold label that, after oxidative gold metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a single-use carbon-based screen-printed electrode (SPE). The use of disposable electrodes allows for simplified measurement in 35 microL of solution. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) and a concentration as low as 3 x 10(-12) M was determined, which is competitive with colorimetric ELISA or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is related to the sensitive ASV determination of gold(III) at a SPE (detection limit of 5 x 10(-9) M) and to the release of a large number of gold(III) ions from each gold particle anchored on the immunocomplex (e.g., 1.7 x 10(5) gold atoms are theoretically contained in a 18-nm spherical gold particle).

  8. Terahertz Conductivity within Colloidal CsPbBr3 Perovskite Nanocrystals: Remarkably High Carrier Mobilities and Large Diffusion Lengths.

    Science.gov (United States)

    Yettapu, Gurivi Reddy; Talukdar, Debnath; Sarkar, Sohini; Swarnkar, Abhishek; Nag, Angshuman; Ghosh, Prasenjit; Mandal, Pankaj

    2016-08-10

    Colloidal CsPbBr3 perovskite nanocrystals (NCs) have emerged as an excellent light emitting material in last one year. Using time domain and time-resolved THz spectroscopy and density functional theory based calculations, we establish 3-fold free carrier recombination mechanism, namely, nonradiative Auger, bimolecular electron-hole recombination, and inefficient trap-assisted recombination in 11 nm sized colloidal CsPbBr3 NCs. Our results confirm a negligible influence of surface defects in trapping charge carriers, which in turn results into desirable intrinsic transport properties, from the perspective of device applications, such as remarkably high carrier mobility (∼4500 cm(2) V(-1) s(-1)), large diffusion length (>9.2 μm), and high luminescence quantum yield (80%). Despite being solution processed and possessing a large surface to volume ratio, this combination of high carrier mobility and diffusion length, along with nearly ideal photoluminescence quantum yield, is unique compared to any other colloidal quantum dot system.

  9. Solar Cells Based on Inks of n-Type Colloidal Quantum Dots

    KAUST Repository

    Ning, Zhijun

    2014-10-28

    © 2014 American Chemical Society. New inorganic ligands including halide anions have significantly accelerated progress in colloidal quantum dot (CQD) photovoltaics in recent years. All such device reports to date have relied on halide treatment during solid-state ligand exchanges or on co-treatment of long-aliphatic-ligand-capped nanoparticles in the solution phase. Here we report solar cells based on a colloidal quantum dot ink that is capped using halide-based ligands alone. By judicious choice of solvents and ligands, we developed a CQD ink from which a homogeneous and thick colloidal quantum dot solid is applied in a single step. The resultant films display an n-type character, making it suitable as a key component in a solar-converting device. We demonstrate two types of quantum junction devices that exploit these iodide-ligand-based inks. We achieve solar power conversion efficiencies of 6% using this class of colloids.

  10. Colloidal Electrolytes and the Critical Micelle Concentration

    Science.gov (United States)

    Knowlton, L. G.

    1970-01-01

    Describes methods for determining the Critical Micelle Concentration of Colloidal Electrolytes; methods described are: (1) methods based on Colligative Properties, (2) methods based on the Electrical Conductivity of Colloidal Electrolytic Solutions, (3) Dye Method, (4) Dye Solubilization Method, and (5) Surface Tension Method. (BR)

  11. A New Biosensor for Hydrogen Peroxide Based on Ag Colloid ...

    African Journals Online (AJOL)

    The sensor was highly sensitive to H2O2 with a detection limit of 1.0 x 10-6 M and the sensor achieved 95% of the steady-state current within 5 s. The sensor exhibited high sensitivity and stability. Keywords: Horseradish peroxidase; Ag colloid; Azure C; Hydrogen peroxide. South African Journal of Chemistry Vol.58 2005: 4- ...

  12. Colloidal polyaniline

    Science.gov (United States)

    Armes, Steven P.; Aldissi, Mahmoud

    1990-01-01

    Processable electrically conductive latex polymer compositions including colloidal particles of an oxidized, polymerized amino-substituted aromatic monomer, a stabilizing effective amount of a random copolymer containing amino-benzene type moieties as side chain constituents, and dopant anions, and a method of preparing such polymer compositions are provided.

  13. Biocompatible Colloidal Suspensions Based on Magnetic Iron Oxide Nanoparticles: Synthesis, Characterization and Toxicological Profile

    Science.gov (United States)

    Coricovac, Dorina-Elena; Moacă, Elena-Alina; Pinzaru, Iulia; Cîtu, Cosmin; Soica, Codruta; Mihali, Ciprian-Valentin; Păcurariu, Cornelia; Tutelyan, Victor A.; Tsatsakis, Aristidis; Dehelean, Cristina-Adriana

    2017-01-01

    The use of magnetic iron oxide nanoparticles in biomedicine has evolved intensely in the recent years due to the multiple applications of these nanomaterials, mainly in domains like cancer. The aim of the present study was: (i) to develop biocompatible colloidal suspensions based on magnetic iron oxide nanoparticles as future theranostic tools for skin pathology and (ii) to test their effects in vitro on human keratinocytes (HaCat cells) and in vivo by employing an animal model of acute dermal toxicity. Biocompatible colloidal suspensions were obtained by coating the magnetic iron oxide nanoparticles resulted during the solution combustion synthesis with a double layer of oleic acid, as innovative procedure in increasing bioavailability. The colloidal suspensions were characterized in terms of dynamic light scattering (DLS) and transmission electron microscopy (TEM). The in vitro effects of these suspensions were tested by means of Alamar blue assay and the noxious effects at skin level were measured using non-invasive methods. The in vitro results indicated a lack of toxicity on normal human cells induced by the iron oxide nanoparticles colloidal suspensions after an exposure of 24 h to different concentrations (5, 10, and 25 μg·mL−1). The dermal acute toxicity test showed that the topical applications of the colloidal suspensions on female and male SKH-1 hairless mice were not associated with significant changes in the quality of barrier skin function. PMID:28400730

  14. DSC and conductivity studies on PVA based proton conducting gel ...

    Indian Academy of Sciences (India)

    Unknown

    An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH4SCN) solution and characterize ... dependence of ionic conductivity exhibits VTF behaviour. Keywords. Polymer gel electrolytes; ionic conductivity; solvent free polymer ...

  15. A novel wound rinsing solution based on nano colloidal silver

    Directory of Open Access Journals (Sweden)

    Soheila Kordestani

    2014-10-01

    Full Text Available Objective(s: The present study aimed to investigate the antiseptic properties of a colloidal nano silver wound rinsing solution to inhibit a wide range of pathogens including bacteria, viruses and fungus present in chronic and acute wounds. Materials and Methods:The wound rinsing solution named SilvoSept® was prepared using colloidal nano silver suspension. Physicochemical properties, effectiveness against microorganism including  Staphylocoocous aureus ATCC 6538P, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739 ,Candida albicans ATCC 10231, Aspergillus niger ATCC 16404, MRSA , Mycobacterium spp. , HSV-1 and H1N1, and biocompatibility tests were carried out according to relevant standards . Results: X-ray diffraction (XRD scan was performed on the sample and verify single phase of silver particles in the compound. The size of the silver particles in the solution, measured by dynamic light scattering (DLS techniqu, ranged 80-90 nm. Transmission electron microscopy (TEM revealed spherical shape with smooth surface of the silver nanoparticles. SilvoSept® reduced 5 log from the initial count of 107 CFU/mL of Staphylocoocous aureus ATCC 6538P, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 8739, Candida albicans ATCC 10231, Aspergillus niger ATCC 16404, MRSA, Mycobacterium spp. Further assessments of SilvoSept solution exhibited a significant inhibition on the replication of HSV-1 and H1N1. The biocompatibility studies showed that the solution was non-allergic, non-irritant and noncytotoxic. Conclusion: Findings of the present study showed that SilvoSept® wound rinsing solution containing nano silver particles is an effective antiseptic solution against a wide spectrum of microorganism. This compound can be a suitable candidate for wound irrigation.   

  16. Effect of stagnant-layer conductivity on the electric permittivity of concentrated colloidal suspensions.

    Science.gov (United States)

    Carrique, F; Arroyo, F J; Shilov, V N; Cuquejo, J; Jiménez, M L; Delgado, A V

    2007-03-14

    A long-lasting experience in the electrokinetics of suspensions has shown that the so-called standard model may be partly in error in explaining experimental data. In this model, the stagnant layer is considered nonconducting (Ksigmai=0), and only the diffuse layer contributes to the total surface conductivity (Ksigma=Ksigmad). In the present work, the authors analyze the consequences of assuming a nonzero stagnant layer conductivity on the permittivity of concentrated suspensions. Using a cell model to account for the particle-particle interactions, and a well established ion adsorption isotherm on the inner region of the double layer, the authors find the frequency-dependent electric permittivity of suspensions of spherical particles with volume fractions of solids up to above 40%. It is demonstrated that the addition of Ksigmai significantly increases the contributions of the double layer to the polarization of the suspension: the alpha or concentration polarization at low (kilohertz) frequencies, and the Maxwell-Wagner-O'Konski (associated with conductivity mismatch between particle and medium) one at intermediate (megahertz) frequencies. While checking for the possibility that the results obtained in conditions of Ksigmai not equal 0 could be reproduced assuming Ksigmai=0 and raising Ksigmad to reach identical total Ksigma, it is found that this is approximately possible in the calculation of the permittivity. Interestingly, this does not occur in the case of electrophoretic mobility, where the situations Ksigma=Ksigmad and Ksigma=Ksigmad+Ksigmai (for equal Ksigma) can be distinguished for all frequencies. This points to the importance of using more than one electrokinetic technique to properly evaluate not only the zeta potential but other transport properties of concentrated suspensions, particularly Ksigmai.

  17. Zein-based colloidal particles for encapsulation and delivery of epigallocatechin gallate

    NARCIS (Netherlands)

    Donsì, F.; Voudouris, P.; Veen, S.J.; Velikov, K.P.

    Zein, a water insoluble plant protein from a renewable natural source, has been identified as a highly promising material for the production of protein-based colloidal particles for the encapsulation of lipophilic compounds. However, the encapsulation of hydrophilic, water-soluble, bioactive

  18. Colloidal nematostatics

    Directory of Open Access Journals (Sweden)

    V.M. Pergamenshchik

    2010-01-01

    Full Text Available We give a review of the theory of large distance colloidal interaction via the nematic director field. The new area of nematic colloidal systems (or nematic emulsions has been guided by the analogy between the colloidal nematostatics and electrostatics. The elastic charge density representation of the colloidal nematostatics [V.M. Pergamenshchik, V.O. Uzunova, Eur. Phys. J. E, 2007, 23, 161; Phys. Rev. E, 2007, 76, 011707] develops this analogy at the level of charge density and Coulomb interaction. The analogy is shown to lie in common mathematics based on the solutions of Laplace equation. However, the 3d colloidal nematostatics substantially differs from electrostatics both in its mathematical structure and physical implications. The elastic charge is a vector fully determined by the torque exerted upon colloid, the role of Gauss' theorem is played by conservation of the torque components. Elastic multipoles consist of two tensors (dyads. Formulas for the elastic multipoles, the Coulomb-like, dipole-dipole, and quadrupole-quadrupole pair interaction potentials are derived and illustrated by particular examples. Based on the tensorial structure, we list possible types of elastic dipoles and quadrupoles. An elastic dipole is characterized by its isotropic strength, anisotropy, chirality, and its longitudinal component. An elastic quadrupole can be uniaxial and biaxial. Relation between the multipole type and its symmetry is discussed, sketches of some types of multipoles are given. Using the mirror image method of electrostatics as a guiding idea, we develop the mirror image method in nematostatics for arbitrary director tilt at the wall. The method is applied to the charge-wall and dipole-wall interaction.

  19. Colloidal CuInSe2 nanocrystals: from gradient stoichiometry toward homogeneous alloyed structure mediated by conducting polymer P3HT.

    Science.gov (United States)

    Liang, Yen Nan; Yu, Kui; Yan, Qingyu; Hu, Xiao

    2013-05-22

    We report, for the first time, the synthesis of colloidal copper indium selenide (CuInSe2) nanocrystals (NCs) possessing a gradient stoichiometry that is potentially tunable by the presence of a conducting polymer, i.e., poly(3-hexyl thiophene) (P3HT) in the synthesis medium. Dibenzyl ether (DBE) was used as a reaction medium, whereas copper acetylacetonate (Cu(acac)2), indium acetylacetonate (In(acac)3), and selenium powder were used as Cu, In, and Se sources, respectively. The Se precursor was tri-n-octylphosphine selenide (TOP-Se). Without the presence of P3HT, the resulting NCs consist of a p-type (Cu(1+) rich) core and an n-type (In(3+) rich) shell. Such a gradient stoichiometry was moderated to be substantially more homogeneous because the presence of P3HT is believed to have significantly reduced the reactivity difference between Cu(acac)2 and In(acac)3, as well as and their respective monomers. Furthermore, the P3HT also acts as a surface coordination species, contributing to the readily preparation of conducting polymer-NCs hybrids by a single-step synthesis. The understandings of this work can serve as a guide for design and synthesis of conducting polymer-NCs hybrids based on various ternary or quaternary compound semiconductors with different core-shell composition gradient.

  20. Radioactive colloids

    International Nuclear Information System (INIS)

    Bergqvist, L.

    1987-01-01

    Different techniques for the characterization of radioactive colloids, used in nuclear medicine, have been evaluated and compared. Several radioactive colloids have been characterized in vitro and in vivo and tested experimentally. Colloid biokinetics following interstitial or intravenous injection were evaluated with a scintillation camera technique. Lymphoscintigraphy with a Tc-99-labelled antimony sulphur colloid was performed in 32 patients with malignant melanoma in order to evaluate the technique. Based on the biokinetic results, absorbed doses in tissues and organs were calculated. The function of the reticuloendothelial system has been evaluated in rats after inoculation with tumour cells. Microfiltration and photon correlation spectroscopy were found to be suitable in determining activity-size and particle size distributions, respectively. Maximal lymph node uptake following subcutaneous injection was found to correspond to a colloid particle size between 10 and 50 nm. Lymphoscintigraphy was found to be useful in the study of lymphatic drainage from the primary tumour site in patients with malignant melanoma on the trunk. Quantitative analysis of ilio-inguinal lymph node uptake in patients with malignant melanoma on the lower extremities was, however, found to be of no value for the detection of metastatic disease in lymph nodes. High absorbed doses may be received in lymph nodes (up to 1 mGy/MBq) and at the injection site (about 10 mGy/MBq). In an experimental study it was found that the relative colloid uptake in bone marrow and spleen depended on the total number of intravenously injected particles. This may considerably affect the absorbed dose in these organs. (author)

  1. Assembling nanoparticle coatings to improve the drug delivery performance of lipid based colloids.

    Science.gov (United States)

    Simovic, Spomenka; Barnes, Timothy J; Tan, Angel; Prestidge, Clive A

    2012-02-21

    Lipid based colloids (e.g. emulsions and liposomes) are widely used as drug delivery systems, but often suffer from physical instabilities and non-ideal drug encapsulation and delivery performance. We review the application of engineered nanoparticle layers at the interface of lipid colloids to improve their performance as drug delivery systems. In addition we focus on the creation of novel hybrid nanomaterials from nanoparticle-lipid colloid assemblies and their drug delivery applications. Specifically, nanoparticle layers can be engineered to enhance the physical stability of submicron lipid emulsions and liposomes, satbilise encapsulated active ingredients against chemical degradation, control molecular transport and improve the dermal and oral delivery characteristics, i.e. increase absorption, bioavailability and facilitate targeted delivery. It is feasible that hybrid nanomaterials composed of nanoparticles and colloidal lipids are effective encapsulation and delivery systems for both poorly soluble drugs and biological drugs and may form the basis for the next generation of medicines. Additional pre-clinical research including specific animal model studies are required to advance the peptide/protein delivery systems, whereas the silica lipid hybrid systems have now entered human clinical trials for poorly soluble drugs. This journal is © The Royal Society of Chemistry 2012

  2. Microwave-Assisted Size Control of Colloidal Nickel Nanocrystals for Colloidal Nanocrystals-Based Non-volatile Memory Devices

    Science.gov (United States)

    Yadav, Manoj; Velampati, Ravi Shankar R.; Mandal, D.; Sharma, Rohit

    2018-03-01

    Colloidal synthesis and size control of nickel (Ni) nanocrystals (NCs) below 10 nm are reported using a microwave synthesis method. The synthesised colloidal NCs have been characterized using x-ray diffraction, transmission electron microscopy (TEM) and dynamic light scattering (DLS). XRD analysis highlights the face centred cubic crystal structure of synthesised NCs. The size of NCs observed using TEM and DLS have a distribution between 2.6 nm and 10 nm. Furthermore, atomic force microscopy analysis of spin-coated NCs over a silicon dioxide surface has been carried out to identify an optimum spin condition that can be used for the fabrication of a metal oxide semiconductor (MOS) non-volatile memory (NVM) capacitor. Subsequently, the fabrication of a MOS NVM capacitor is reported to demonstrate the potential application of colloidal synthesized Ni NCs in NVM devices. We also report the capacitance-voltage (C-V) and capacitance-time (C-t) response of the fabricated MOS NVM capacitor. The C-V and C-t characteristics depict a large flat band voltage shift (V FB) and high retention time, respectively, which indicate that colloidal Ni NCs are excellent candidates for applications in next-generation NVM devices.

  3. Preparation and characterization of zirconium based colloidal suspensions; Preparacao e caracterizacao de suspensoes coloidais a base de zirconio

    Energy Technology Data Exchange (ETDEWEB)

    Chiavacci, Leila Aparecida; Pulcinelli, Sandra Helena; Santilli, Celso Valentim [UNESP, Araraquara, SP (Brazil). Inst. de Quimica

    1995-12-31

    Attention has been paid to zirconia based ceramic materials due to its technological applications, like catalysts, ionic changers, sensors, etc. Colloidal suspensions based on zirconium, containing different cation/anion molar ratio, have been prepared aiming the improvement of its extrinsical properties. The systems have been characterized by turbidimetry and the xerogels have been analysed by scanning electronic microscopy, infrared spectroscopy and x-ray diffraction. Results make evident the viability of preparation of transparent colloidal suspensions, gel and powders, in which the particles size and morphology could be controlled. (author) 3 figs.

  4. Photojunction Field-Effect Transistor Based on a Colloidal Quantum Dot Absorber Channel Layer

    KAUST Repository

    Adinolfi, Valerio

    2015-01-27

    © 2015 American Chemical Society. The performance of photodetectors is judged via high responsivity, fast speed of response, and low background current. Many previously reported photodetectors based on size-tuned colloidal quantum dots (CQDs) have relied either on photodiodes, which, since they are primary photocarrier devices, lack gain; or photoconductors, which provide gain but at the expense of slow response (due to delayed charge carrier escape from sensitizing centers) and an inherent dark current vs responsivity trade-off. Here we report a photojunction field-effect transistor (photoJFET), which provides gain while breaking prior photoconductors\\' response/speed/dark current trade-off. This is achieved by ensuring that, in the dark, the channel is fully depleted due to a rectifying junction between a deep-work-function transparent conductive top contact (MoO3) and a moderately n-type CQD film (iodine treated PbS CQDs). We characterize the rectifying behavior of the junction and the linearity of the channel characteristics under illumination, and we observe a 10 μs rise time, a record for a gain-providing, low-dark-current CQD photodetector. We prove, using an analytical model validated using experimental measurements, that for a given response time the device provides a two-orders-of-magnitude improvement in photocurrent-to-dark-current ratio compared to photoconductors. The photoJFET, which relies on a junction gate-effect, enriches the growing family of CQD photosensitive transistors.

  5. Colloidal processing of Fe-based metal ceramic composites with high content of ceramic reinforcement

    Energy Technology Data Exchange (ETDEWEB)

    Escribano, J. A.; Ferrari, B.; Alvaredo, P.; Gordo, E.; Sanchez-Herencia, A. J.

    2013-07-01

    Major difficulties of processing metal-matrix composites by means of conventional powder metallurgy techniques are the lack of dispersion of the phases within the final microstructure. In this work, processing through colloidal techniques of the Fe-based metal-matrix composites, with a high content of a ceramic reinforcement (Ti(C,N) ), is presented for the first time in the literature. The colloidal approach allows a higher control of the powders packing and a better homogenization of phases since powders are mixed in a liquid medium. The chemical stability of Fe in aqueous medium determines the dispersion conditions of the mixture. The Fe slurries were formulated by optimising their zeta potential and their rheology, in order to shape bulk pieces by slip-casting. Preliminary results demonstrate the viability of this procedure, also opening new paths to the microstructural design of fully sintered Fe-based hard metal, with 50 vol. % of Ti(C,N) in its composition. (Author)

  6. Gravure-printed ammonia sensor based on organic polyaniline colloids

    Czech Academy of Sciences Publication Activity Database

    Syrový, T.; Kuberský, P.; Sapurina, Irina; Pretl, S.; Bober, Patrycja; Syrová, L.; Hamáček, A.; Stejskal, Jaroslav

    2016-01-01

    Roč. 225, 31 March (2016), s. 510-516 ISSN 0925-4005 R&D Projects: GA MŠk(CZ) LH14199; GA TA ČR(CZ) TE01020022 Institutional support: RVO:61389013 Keywords : ammonia gas * polyaniline * conducting polymer Subject RIV: CG - Electrochemistry Impact factor: 5.401, year: 2016

  7. New polyelectrolyte complex particles as colloidal dispersions based on weak synthetic and/or natural polyelectrolytes

    Directory of Open Access Journals (Sweden)

    2011-06-01

    Full Text Available This study aims to evidence the formation of stable polyelectrolyte complex particles as colloidal dispersions using some weak polyelectrolytes: chitosan and poly(allylamine hydrochloride as polycations and poly(acrylic acid (PAA and poly(2-acrylamido-2-methylpropanesulfonic acid – co – acrylic acid (PAMPSAA as polyanions. Polyelectrolyte complex particles as colloidal dispersion were prepared by controlled mixing of the oppositely charged polymers, with a constant addition rate. The influences of the polyelectrolytes structure and the molar ratio between ionic charges on the morphology, size, and colloidal stability of the complex particles have been deeply investigated by turbidimetry, dynamic light scattering and atomic force microscopy. A strong influence of polyanion structure on the values of molar ratio n–/n+ when neutral complex particles were obtained has been noticed, which shifts from the theoretical value of 1.0, observed when PAA was used, to 0.7 for PAMPSAA based complexes. The polyions chain characteristics influenced the size and shape of the complexes, larger particles being obtained when chitosan was used, for the same polyanion, and when PAMPSAA was used, for the same polycation.

  8. A colloidoscope of colloid-based porous materials and their uses.

    Science.gov (United States)

    Phillips, Katherine R; England, Grant T; Sunny, Steffi; Shirman, Elijah; Shirman, Tanya; Vogel, Nicolas; Aizenberg, Joanna

    2016-01-21

    Nature evolved a variety of hierarchical structures that produce sophisticated functions. Inspired by these natural materials, colloidal self-assembly provides a convenient way to produce structures from simple building blocks with a variety of complex functions beyond those found in nature. In particular, colloid-based porous materials (CBPM) can be made from a wide variety of materials. The internal structure of CBPM also has several key attributes, namely porosity on a sub-micrometer length scale, interconnectivity of these pores, and a controllable degree of order. The combination of structure and composition allow CBPM to attain properties important for modern applications such as photonic inks, colorimetric sensors, self-cleaning surfaces, water purification systems, or batteries. This review summarizes recent developments in the field of CBPM, including principles for their design, fabrication, and applications, with a particular focus on structural features and materials' properties that enable these applications. We begin with a short introduction to the wide variety of patterns that can be generated by colloidal self-assembly and templating processes. We then discuss different applications of such structures, focusing on optics, wetting, sensing, catalysis, and electrodes. Different fields of applications require different properties, yet the modularity of the assembly process of CBPM provides a high degree of tunability and tailorability in composition and structure. We examine the significance of properties such as structure, composition, and degree of order on the materials' functions and use, as well as trends in and future directions for the development of CBPM.

  9. Nanocomposites Based on Luminescent Colloidal Nanocrystals and Polymeric Ionic Liquids towards Optoelectronic Applications

    Directory of Open Access Journals (Sweden)

    Annamaria Panniello

    2014-01-01

    Full Text Available Polymeric ionic liquids (PILs are an interesting class of polyelectrolytes, merging peculiar physical-chemical features of ionic liquids with the flexibility, mechanical stability and processability typical of polymers. The combination of PILs with colloidal semiconducting nanocrystals leads to novel nanocomposite materials with high potential for batteries and solar cells. We report the synthesis and properties of a hybrid nanocomposite made of colloidal luminescent CdSe nanocrystals incorporated in a novel ex situ synthesized imidazolium-based PIL, namely, either a poly(N-vinyl-3-butylimidazolium hexafluorophosphate or a homologous PIL functionalized with a thiol end-group exhibiting a chemical affinity with the nanocrystal surface. A capping exchange procedure has been implemented for replacing the pristine organic capping molecules of the colloidal CdSe nanocrystals with inorganic chalcogenide ions, aiming to disperse the nano-objects in the PILs, by using a common polar solvent. The as-prepared nanocomposites have been studied by TEM investigation, UV-Vis, steady-state and time resolved photoluminescence spectroscopy for elucidating the effects of the PIL functionalization on the morphological and optical properties of the nanocomposites.

  10. Colloidal organization

    CERN Document Server

    Okubo, Tsuneo

    2015-01-01

    Colloidal Organization presents a chemical and physical study on colloidal organization phenomena including equilibrium systems such as colloidal crystallization, drying patterns as an example of a dissipative system and similar sized aggregation. This book outlines the fundamental science behind colloid and surface chemistry and the findings from the author's own laboratory. The text goes on to discuss in-depth colloidal crystallization, gel crystallization, drying dissipative structures of solutions, suspensions and gels, and similar-sized aggregates from nanosized particles. Special emphas

  11. Colloidal dispersions of conducting copolymers of aniline and p-phenylenediamine for films with enhanced conductometric sensitivity to temperature

    Czech Academy of Sciences Publication Activity Database

    Li, Yu; Bober, Patrycja; Trchová, Miroslava; Stejskal, Jaroslav

    2017-01-01

    Roč. 5, č. 7 (2017), s. 1668-1674 ISSN 2050-7526 R&D Projects: GA ČR(CZ) GP14-05568P Institutional support: RVO:61389013 Keywords : colloids * polyaniline * poly(p-phenylenediamine) Subject RIV: JI - Composite Materials OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics Impact factor: 5.256, year: 2016

  12. PbSe-Based Colloidal Core/Shell Heterostructures for Optoelectronic Applications

    Science.gov (United States)

    Zaiats, Gary; Yanover, Diana; Vaxenburg, Roman; Tilchin, Jenya; Sashchiuk, Aldona; Lifshitz, Efrat

    2014-01-01

    Lead-based (IV–VI) colloidal quantum dots (QDs) are of widespread scientific and technological interest owing to their size-tunable band-gap energy in the near-infrared optical region. This article reviews the synthesis of PbSe-based heterostructures and their structural and optical investigations at various temperatures. The review focuses on the structures consisting of a PbSe core coated with a PbSexS1–x (0 ≤ x ≤ 1) or CdSe shell. The former-type shells were epitaxially grown on the PbSe core, while the latter-type shells were synthesized using partial cation-exchange. The influence of the QD composition and the ambient conditions, i.e., exposure to oxygen, on the QD optical properties, such as radiative lifetime, Stokes shift, and other temperature-dependent characteristics, was investigated. The study revealed unique properties of core/shell heterostructures of various compositions, which offer the opportunity of fine-tuning the QD electronic structure by changing their architecture. A theoretical model of the QD electronic band structure was developed and correlated with the results of the optical studies. The review also outlines the challenges related to potential applications of colloidal PbSe-based heterostructures. PMID:28788244

  13. Colloidal stability of iron oxide nanocrystals coated with a PEG-based tetra-catechol surfactant.

    Science.gov (United States)

    Mondini, Sara; Drago, Carmelo; Ferretti, Anna M; Puglisi, Alessandra; Ponti, Alessandro

    2013-03-15

    Long-term colloidal stability of magnetic iron oxide nanoparticles (NPs) is an important goal that has not yet been fully achieved. To make an advance in our understanding of the colloidal stability of iron oxide NPs in aqueous media, we prepared NPs comprising a monodisperse (13 nm) iron oxide core coated with a PEG-based (PEG: polyethyleneglycol) surfactant. This consists of a methoxy-terminated PEG chain (MW = 5000 Da) bearing four catechol groups via a diethylenetriamine linker. The surfactant was grafted onto the nanocrystals by ligand exchange monitored by infrared spectroscopy. The colloidal stability of these nanoparticles was probed by monitoring the time evolution of the Z-average intensity-weighted radius R(h) and volume-weighted size distribution P(v) obtained from analysis of dynamic light scattering data. The nanoparticles showed no sign of aggregation for four months in deionized water at room temperature and also when subjected to thermal cycling between 25 and 75 °C. In 0.01 M PBS (phosphate buffered saline), aggregation (if any) is slow and partial; after 66 h, about 50% of NPs have not aggregated. Aggregation is more effective in 0.15 M NH(4)AcO buffer, where isolated particles are not observed after 66 h, and especially in acidic NH(4)AcO/AcOH buffer, where aggregation is complete within 1 h and precipitation is observed. The differing stability of the NPs in the above aqueous media is closely related to their ζ potential.

  14. Low frequency dielectric relaxation processes and ionic conductivity of montmorillonite clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone−ethylene glycol blends

    Directory of Open Access Journals (Sweden)

    2008-11-01

    Full Text Available The dielectric dispersion behaviour of montmorillonite (MMT clay nanoparticles colloidal suspension in poly(vinyl pyrrolidone-ethylene glycol (PVP-EG blends were investigated over the frequency range 20 Hz to 1 MHz at 30°C. The 0, 1, 2, 3, 5 and 10 wt% MMT clay concentration of the weight of total solute (MMT+PVP were prepared in PVP-EG blends using EG as solvent. The complex relative dielectric function, alternating current (ac electrical conductivity, electric modulus and impedance spectra of these materials show the relaxation processes corresponding to the micro-Brownian motion of PVP chain, ion conduction and electrode polarization phenomena. The real part of ac conductivity spectra of these materials obeys Jonscher power law σ′(ω =σdc + Aωn in upper frequency end of the measurement, whereas dispersion in lower frequency end confirms the presence of electrode polarization effect. It was observed that the increase of clay concentration in the PVP-EG blends significantly increases the ac conductivity values, and simultaneously reduces the ionic conductivity relaxation time and electric double layer relaxation time, which suggests that PVP segmental dynamics and ionic motion are strongly coupled. The intercalation of EG structures in clay galleries and exfoliation of clay sheets by adsorption of PVP-EG structures on clay surfaces are discussed by considering the hydrogen bonding interactions between the hydroxyl group (–OH of EG molecules, carbonyl group (C=O of PVP monomer units, and the hydroxylated aluminate surfaces of the MMT clay particles. Results suggest that the colloidal suspension of MMT clay nano particles in the PVP-EG blends provide a convenient way to obtain an electrolyte solution with tailored electrical conduction properties.

  15. Pt based PEMFC catalysts prepared from colloidal particle suspensions--a toolbox for model studies.

    Science.gov (United States)

    Speder, Jozsef; Altmann, Lena; Roefzaad, Melanie; Bäumer, Marcus; Kirkensgaard, Jacob J K; Mortensen, Kell; Arenz, Matthias

    2013-03-14

    A colloidal synthesis approach is presented that allows systematic studies of the properties of supported proton exchange membrane fuel cell (PEMFC) catalysts. The applied synthesis route is based on the preparation of monodisperse nanoparticles in the absence of strong binding organic stabilizing agents. No temperature post-treatment of the catalyst is required rendering the synthesis route ideally suitable for comparative studies. We report work concerning a series of catalysts based on the same colloidal Pt nanoparticle (NP) suspension, but with different high surface area (HSA) carbon supports. It is shown that for the prepared catalysts the carbon support has no catalytic co-function, but carbon pre-treatment leads to enhanced sticking of the Pt NPs on the support. An unwanted side effect, however, is NP agglomeration during synthesis. By contrast, enhanced NP sticking without agglomeration can be accomplished by the addition of an ionomer to the NP suspension. The catalytic activity of the prepared catalysts for the oxygen reduction reaction is comparable to industrial catalysts and no influence of the particle size is found in the range of 2-5 nm.

  16. A new method for municipal solid waste incinerator (MSWI) fly ash inertization, based on colloidal silica.

    Science.gov (United States)

    Bontempi, E; Zacco, A; Borgese, L; Gianoncelli, A; Ardesi, R; Depero, L E

    2010-11-01

    Municipal solid waste incineration (MSWI) is a straightforward way to manage waste, however the disposal of process byproducts, mainly bottom and fly ash, is still a problem, because of their hazardous contents. Fly ash is a byproduct of many other processes that involve combustion to produce energy. In this paper we present and discuss a new method for MSWI fly ash inertization, mainly based on the use of colloidal silica as a stabilization agent for metals. In the patented procedure, fly ash of different provenance can be used to produce an inert and non-hazardous material, that can be reused. In fact to make the recovery process more efficient, landfilling should be totally avoided. For this reason, to enhance the possibility of reuse, a washing process, for salts recovery, is proposed as a final step of the inertization procedure. The obtained inert material is called COSMOS (COlloidal Silica Medium to Obtain Safe inert), and it is composed of calcium carbonate, calcium sulfate, silicon oxide and a wide quantity of non-soluble amorphous compounds. COSMOS does not contain any corrosive salts. This makes it extremely interesting for cement industry applications with several other advantages, and environmental benefits. The new proposed inertization procedure appears very promising, because it allows MSWI fly ash to be considered a valuable resource. Thanks to the obtained results, a demonstration project, in the frame of LIFE+, has been funded by the European Commission (LIFE+ 2008 project ENV/IT/000434, ).

  17. Synthesis of colloids based on gold nanoparticles dispersed in castor oil

    International Nuclear Information System (INIS)

    Silva, E. C. da; Silva, M. G. A. da; Meneghetti, S. M. P.; Machado, G.; Alencar, M. A. R. C.; Hickmann, J. M.; Meneghetti, M. R.

    2008-01-01

    New colloidal solutions of gold nanoparticles (AuNP), using castor oil as a nontoxic organic dispersant agent, were prepared via three different methods. In all three cases, tetrachloroauric(III) acid was employed as the gold source. The colloids were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). The AuNP produced by the three methods were quasispherical in shape, however with different average sizes. The individual characteristics of the nanoparticles presented in each colloidal system were also confirmed by observation of absorption maxima at different wavelengths of visible light. Each method of synthesis leads to colloids with different grades of stability with respect to particle agglomeration.

  18. Effects of intravenous solutions on acid-base equilibrium: from crystalloids to colloids and blood components.

    Science.gov (United States)

    Langer, Thomas; Ferrari, Michele; Zazzeron, Luca; Gattinoni, Luciano; Caironi, Pietro

    2014-01-01

    Intravenous fluid administration is a medical intervention performed worldwide on a daily basis. Nevertheless, only a few physicians are aware of the characteristics of intravenous fluids and their possible effects on plasma acid-base equilibrium. According to Stewart's theory, pH is independently regulated by three variables: partial pressure of carbon dioxide, strong ion difference (SID), and total amount of weak acids (ATOT). When fluids are infused, plasma SID and ATOT tend toward the SID and ATOT of the administered fluid. Depending on their composition, fluids can therefore lower, increase, or leave pH unchanged. As a general rule, crystalloids having a SID greater than plasma bicarbonate concentration (HCO₃-) cause an increase in plasma pH (alkalosis), those having a SID lower than HCO₃- cause a decrease in plasma pH (acidosis), while crystalloids with a SID equal to HCO₃- leave pH unchanged, regardless of the extent of the dilution. Colloids and blood components are composed of a crystalloid solution as solvent, and the abovementioned rules partially hold true also for these fluids. The scenario is however complicated by the possible presence of weak anions (albumin, phosphates and gelatins) and their effect on plasma pH. The present manuscript summarises the characteristics of crystalloids, colloids, buffer solutions and blood components and reviews their effect on acid-base equilibrium. Understanding the composition of intravenous fluids, along with the application of simple physicochemical rules best described by Stewart's approach, are pivotal steps to fully elucidate and predict alterations of plasma acid-base equilibrium induced by fluid therapy.

  19. Preparation and characterization of nano-composites with carbon nanotubes and core-shell type polyaniline for the conductive colloidal ink

    Science.gov (United States)

    Lee, Jungmin; Varadan, Vijay K.

    2012-04-01

    Printing method for electronics elements fabrication has attractive advantages such as low material consumption, high speed fabrication, and low temperature process. The stable conductive ink is the most important factor for the fabrication of printed electronics elements with high resolution. These materials are widely used as fillers in conductive inks; metal particles, conductive polymers, and carbon materials. Among these materials, the carbon nanotubes (CNTs) are extremely attractive filler for printed electronics due to its superior electrical properties, extra high mechanical properties, and excellent chemical stability. In this research, nano-composites which are composed of multi wall carbon nanotubes (MWCNTs) and polyaniline core-shell type particles were synthesized and formulated into electrically conductive colloidal inks. The poly(acrylonitrile-co-itaconic acid-co-methylacrylate) nanoparticles were used as cores. And this core was coated with polyaniline. The surface treatments for MWCNTs were applied to make the stable nano-composites. The experimental conditions were optimized to achieve high miscibility between MWCNTs and polyaniline coated particles. Their structure and surface morphology of the nanocomposites were characterized by Scanning Electron Microscopy. And four point probe automatic resistivity meter was used to measure the conductivities of the nanocomposites.

  20. Charge transport and contact resistance in coplanar devices based on colloidal polyaniline dispersion

    Czech Academy of Sciences Publication Activity Database

    Masillamani, A. M.; Peřinka, N.; Hajná, Milena; Stejskal, Jaroslav; Tondelier, D.; Bonnassieux, Y.; Vanel, J.-C.; Geffroy, B.; Mencaraglia, D.

    2016-01-01

    Roč. 54, č. 17 (2016), s. 1710-1716 ISSN 0887-6266 R&D Projects: GA ČR(CZ) GA13-00270S Institutional support: RVO:61389013 Keywords : charge transport * colloidal dispersion * colloids Subject RIV: JI - Composite Materials Impact factor: 2.838, year: 2016

  1. High-throughput fabrication of anti-counterfeiting colloid-based photoluminescent microtags using electrical nanoimprint lithography

    International Nuclear Information System (INIS)

    Diaz, R; Palleau, E; Poirot, D; Sangeetha, N M; Ressier, L

    2014-01-01

    This work demonstrates the excellent capability of the recently developed electrical nanoimprint lithography (e-NIL) technique for quick, high-throughput production of well-defined colloid assemblies on surfaces. This is shown by fabricating micron-sized photoluminescent quick response (QR) codes based on the electrostatic directed trapping (so called nanoxerography process) of 28 nm colloidal lanthanide-doped upconverting NaYF 4 nanocrystals. Influencing experimental parameters have been optimized and the contribution of triboelectrification in e-NIL was evidenced. Under the chosen conditions, more than 300 000 nanocrystal-based QR codes were fabricated on a 4 inch silicon wafer, in less than 15 min. These microtags were then transferred to transparent flexible films, to be easily integrated onto desired products. Invisible to the naked eye, they can be decoded and authenticated using an optical microscopy image of their specific photoluminescence mapping. Beyond this very promising application for product tracking and the anti-counterfeiting strategies, e-NIL nanoxerography, potentially applicable to any types of charged and/or polarizable colloids and pattern geometries opens up tremendous opportunities for industrial scale production of various other kinds of colloid-based devices and sensors. (paper)

  2. Conducting polyheterocycle composites based on porous hosts

    Science.gov (United States)

    Park, J. S.; Ruckenstein, E.

    1992-02-01

    Conducting composites based on porous substrates (cotton fiber, non-woven polypropylene mat and porous crosslinked polystyrene) have been prepared by a two step imbibition technique. First, the substrate was imbibed with a solution of monomer (pyrrole or bithiophene) in acetonitrile, followed by partial drying. Subsequently, the substrate was again imbibed, this time with an oxidant dissolved in a suitable solvent. The polymerization of the monomer inside the host in the presence of the oxidant and the doping of the polymer with the oxidant leads to the conducting composite. The highly hydrophobic and porous crosslinked polystyrene, prepared by the concentrated emulsion polymerization method, is the most efficient. The solvent employed for the oxidant plays a major role. A FeCl3-methanol system and porous crosslinked polystyrene lead to conductivities of polythiophene and polypyrrole based composites of 3.63 and 0.65 S/cm, respectively. Copper perchlorate and iron perchlorate are also suitable oxidants. The environmental and thermal stabilities of polypyrrole based composites are lower than those of polythiophene based composites. The thermal stability of polypyrrole based composites can be enhanced by including a small amount of an organic antioxidant, such as amides or substituted phenols, in the composite.

  3. Colloidal glasses

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Colloidal glasses. Glassy state is attained when system fails to reach equilibrium due to crowding of constituent particles. In molecular glasses, glassy state is reached by rapidly lowering the temperature. In colloidal glasses, glassy state is reached by increasing the ...

  4. Injectable PLGA based Colloidal Gels for Zero-order Dexamethasone Release in Cranial Defects

    Science.gov (United States)

    Wang, Qun; Wang, Jinxi; Lu, Qinghua; Detamore, Michael S.; Berkland, Cory

    2010-01-01

    Bone fillers have emerged as an alternative to the invasive surgery often required to repair skeletal defects. Achieving controlled release from these materials is desired for accelerating healing. Here, oppositely-charged Poly (d,l-lactic-co-glycolic acid) (PLGA) nanoparticles were used to create a cohesive colloidal gel as an injectable drug-loaded filler to promote healing in bone defects. The colloid self-assembled through electrostatic forces resulting in a stable 3-D network that may be extruded or molded to the desired shape. The colloidal gel demonstrated shear-thinning behavior due to the disruption of interparticle interactions as the applied shear force was increased. Once the external force was removed, the cohesive property of the colloidal gel was recovered. Similar reversibility and shear-thinning behavior were also observed in colloidal gels loaded with dexamethasone. Near zero-order dexamethasone release was observed over two months when the drug was encapsulated in PLGA nanoparticles and simply blending the drug with the colloidal gel showed similar kinetics for one month. Surgical placement was facilitated by the pseudoplastic material properties and in vivo observations demonstrated that the PLGA colloidal gels stimulated osteoconductive bone formation in rat cranial bone defects. PMID:20303585

  5. Waveguides in colloidal nanosuspensions

    Science.gov (United States)

    López-Peña, Luis A.; Salazar-Romero, Yadira; Terborg, Roland A.; Hernández-Cordero, Juan; Torres, Juan P.; Volke-Sepúlveda, K.

    2014-09-01

    We present and discuss a set of experiments based on the application of the nonlinear properties of colloidal nanosuspensions to induce waveguides with a high-power CW laser beam (wavelength 532nm) and its use for controlling an additional probe beam. The probe is a CW laser of a different wavelength (632nm), whose power is well below the critical value to induce nonlinear effects in the colloidal medium. We also discuss a technique for the characterization of the induced waveguides.

  6. UHV AFM based colloidal probe studies of adhesive properties of VAlN hard coatings

    Science.gov (United States)

    Wiesing, M.; de los Arcos, T.; Grundmeier, G.

    2018-01-01

    The adhesion of polystyrene (PS) on V0.27Al0.29N0.44 and the related influence of the oxidation states of both surfaces was investigated using X-Ray Photoelectron Spectroscopy (XPS) and Colloidal Force Spectroscopy (CFS) in Ultra-High Vacuum (UHV). Complementary, the intimate relation between the adhesion force, the chemical structure and surface polarizability was investigated by XPS valence band spectroscopy and the calculation of non-retarded Hamaker coefficients using Lifshitz theory based on optical data as derived from Reflection Electron Energy Loss Spectroscopy (REELS) spectra. The combined electron and force spectroscopic analysis of the interaction forces disclosed quantitatively the separation of the adhesion force in van der Waals and Lewis acid-base contributions. Further, the surface polarizability of VAlN was shown to be unaffected by oxygen incorporation due to the formation of an only gradually oxidized surface comprising a range of vanadium oxidation states. In contrast, the adhesion force analysis revealed additional Lewis acid-base interactions between the oxidized and non-oxidized VAlN surfaces and carboxyl groups present in the surface of PS after an oxidative oxygen beam treatment.

  7. Optical conductivity of iron-based superconductors.

    Science.gov (United States)

    Charnukha, A

    2014-06-25

    The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein.

  8. Optical conductivity of iron-based superconductors

    International Nuclear Information System (INIS)

    Charnukha, A

    2014-01-01

    The new family of unconventional iron-based superconductors discovered in 2006 immediately relieved their copper-based high-temperature predecessors as the most actively studied superconducting compounds in the world. The experimental and theoretical effort made in order to unravel the mechanism of superconductivity in these materials has been overwhelming. Although our understanding of their microscopic properties has been improving steadily, the pairing mechanism giving rise to superconducting transition temperatures up to 55 K remains elusive. And yet the hope is strong that these materials, which possess a drastically different electronic structure but similarly high transition temperatures compared to the copper-based compounds, will shed essential new light onto the several-decade-old problem of unconventional superconductivity. In this work we review the current understanding of the itinerant-charge-carrier dynamics in the iron-based superconductors and parent compounds largely based on the optical-conductivity data the community has gleaned over the past seven years using such experimental techniques as reflectivity, ellipsometry, and terahertz transmission measurements and analyze the implications of these studies for the microscopic properties of the iron-based materials as well as the mechanism of superconductivity therein. (topical review)

  9. Colloidal processing of Fe-based metalceramic composites with high content of ceramic reinforcement

    Directory of Open Access Journals (Sweden)

    Escribano, J. A.

    2013-12-01

    Full Text Available Major difficulties of processing metal-matrix composites by means of conventional powder metallurgy techniques are the lack of dispersion of the phases within the final microstructure. In this work, processing through colloidal techniques of the Fe-based metal-matrix composites, with a high content of a ceramic reinforcement (Ti(C,N , is presented for the first time in the literature. The colloidal approach allows a higher control of the powders packing and a better homogenization of phases since powders are mixed in a liquid medium. The chemical stability of Fe in aqueous medium determines the dispersion conditions of the mixture. The Fe slurries were formulated by optimising their zeta potential and their rheology, in order to shape bulk pieces by slip-casting. Preliminary results demonstrate the viability of this procedure, also opening new paths to the microstructural design of fully sintered Fe-based hard metal, with 50 vol. % of Ti(C,N in its composition.Las principales dificultades de procesamiento de materiales compuestos de matriz metálica por medio de técnicas convencionales pulvimetalúrgicas es la falta de dispersión entre fases dentro de la microestructura final. Este trabajo describe por primera vez el procesamiento de materiales compuestos de matriz metálica de Fe, con un alto contenido de un refuerzo cerámico (Ti (C, N, mediante técnicas coloidales. El procesamiento coloidal permite un mayor control sobre el empaquetamiento de polvos y una mejor homogeneización de las fases al mezclarse los polvos en un medio líquido. La estabilidad química del Fe en medio acuoso determina las condiciones de dispersión de la mezcla. Las suspensiones de Fe se formularon mediante la optimización del potencial zeta y de su reología, con el fin de dar forma a piezas compactas por colaje en molde de escayola. Los resultados preliminares mostrados demuestran la viabilidad del proceso, además de abrir nuevas vías al dise

  10. A transparent flexible z-axis sensitive multi-touch panel based on colloidal ITO nanocrystals.

    Science.gov (United States)

    Sangeetha, N M; Gauvin, M; Decorde, N; Delpech, F; Fazzini, P F; Viallet, B; Viau, G; Grisolia, J; Ressier, L

    2015-08-07

    Bottom-up fabrication of a flexible multi-touch panel prototype based on transparent colloidal indium tin oxide (ITO) nanocrystal (NC) films is presented. A series of 7% Sn(4+) doped ITO NCs protected by oleate, octanoate and butanoate ligands are synthesized and characterized by a battery of techniques including, high resolution transmission electron microscopy, X-ray diffraction, (1)H, (13)C and (119)Sn nuclear magnetic resonance spectroscopy, and the related diffusion ordered spectroscopy. Electrical resistivities of transparent films of these NCs assembled on flexible polyethylene terephthalate substrates by convective self-assembly from their suspension in toluene decrease with the ligand length, from 220 × 10(3) for oleate ITO to 13 × 10(3)Ω cm for butanoate ITO NC films. A highly transparent, flexible touch panel based on a matrix of strain gauges derived from the least resistive film of 17 nm butanoate ITO NCs sensitively detects the lateral position (x, y) of the touch as well as its intensity over the z-axis. Being compatible with a stylus or bare/gloved finger, a larger version of this module may be readily implemented in upcoming flexible screens, enabling navigation capabilities over all three axes, a feature highly desired by the display industry.

  11. Current Trends in Volume Replacement Therapy and the Use of Synthetic Colloids in Small Animals—An Internet-Based Survey (2016

    Directory of Open Access Journals (Sweden)

    Ivayla D. Yozova

    2017-09-01

    Full Text Available The use of synthetic colloids (SCs, particularly hydroxyethyl starch (HES, in people has changed in recent years following new evidence raising concerns about their efficacy and safety. Although fluid therapy guidelines for small animals are often extrapolated from human medicine, little information exists on current practice in veterinary medicine. The objective of the present study was to investigate current fluid selection, use of plasma volume expanders including SCs, and recent changes in their use in small animal practice. An Internet-based survey was conducted, inviting veterinarians to report their practices in fluid resuscitation and colloid osmotic pressure support, their choice of SC, and perceived adverse effects and contraindications associated with SC use. There were 1,134 respondents from 42 countries, including 46% general practitioners and 38% diplomates. Isotonic crystalloids, HES, and hypertonic saline were chosen by most respondents for fluid resuscitation, and HES by 75% of respondents for colloid osmotic support. Dextran and gelatin were used by some European respondents. Human serum albumin was used more than canine albumin but 45% of respondents, particularly those from Australia and New Zealand, used no albumin product. The majority (70% of respondents changed their practice regarding SCs in recent years (mostly by limiting their use, largely due to safety concerns. However, only 27% of respondents worked in an institution that had a general policy on SC use. Impaired renal function, coagulopathy, and hypertension were most often considered contraindications; impaired coagulation tests and increased respiratory rate were the most frequently perceived adverse effects. The use of HES remains widespread practice in small animals, regardless of geographic location. Nevertheless, awareness of safety issues and restrictions on the use of SCs imposed in human medicine seems to have prompted a decrease in use of SCs by

  12. Single conducting polymer nanowire based conductometric sensors

    Science.gov (United States)

    Bangar, Mangesh Ashok

    The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against

  13. A smart thermo- and pH-responsive microfiltration membrane based on three-dimensional inverse colloidal crystals.

    Science.gov (United States)

    Yu, Bing; Song, Qianqian; Cong, Hailin; Xu, Xiaodan; Han, Dongwei; Geng, Zhongmin; Zhang, Xiaoyan; Usman, Muhammad

    2017-09-21

    In this paper, a thermo- and pH-responsive microfiltration membrane was prepared based on three-dimensional (3D) inverse colloidal crystals (ICC). To manufacture the smart ICC membrane, the typical thermo-responsive N-isopropylacrylamide (NIPAM) and pH-responsive methacrylic acid (MAA) were polymerized inside silica colloidal crystals. The smart ICC membranes were characterized by SEM, IR and contact angle measurements. Moreover, the permeability of smart microfiltration membrane was carried out by the KCl diffusion tests. The result showed that effective diameter of the polymer ICC membrane can be reversible tuned by temperature and pH. Besides, the functional ICC membrane showed outstanding temperature- and pH-responsive gating property, which was applied to separate particles of different sizes. The savvy environment-responsive gating membranes have potential uses in filtration, separation, purification, sensor and other applications.

  14. A dynamic force balance model for colloidal expansion and its DLVO-based application.

    Science.gov (United States)

    Liu, Longcheng; Moreno, Luis; Neretnieks, Ivars

    2009-01-20

    A force balance model that describes the dynamic expansion of colloidal bentonite gels/sols is presented. The colloidal particles are assumed to consist of one or several thin sheets with the other dimensions much larger than their thickness. The forces considered include van der Waals force, diffuse double layer force, thermal force giving rise to Brownian motion, gravity, as well as friction force. The model results in an expression resembling the instationary diffusion equation but with an immensely variable diffusivity. This diffusivity is strongly influenced by the concentration of counterions as well as by the particle concentration in the colloid gel/sol. The properties of the model are explored and discussed, exemplified by the upward expansion of an originally highly compacted bentonite tablet in a test tube. Examples are presented for a number of cases with ionic concentrations varying between very dilute waters up to several molar of counterions. The volume fraction of particles ranges from 40% to very dilute sols.

  15. Colloidal capsules: nano- and microcapsules with colloidal particle shells.

    Science.gov (United States)

    Bollhorst, Tobias; Rezwan, Kurosch; Maas, Michael

    2017-04-18

    Utilizing colloidal particles for the assembly of the shell of nano- and microcapsules holds great promise for the tailor-made design of new functional materials. Increasing research efforts are devoted to the synthesis of such colloidal capsules, by which the integration of modular building blocks with distinct physical, chemical, or morphological characteristics in a capsule's shell can result in novel properties, not present in previous encapsulation structures. This review will provide a comprehensive overview of the synthesis strategies and the progress made so far of bringing nano- and microcapsules with shells of densely packed colloidal particles closer to application in fields such as chemical engineering, materials science, or pharmaceutical and life science. The synthesis routes are categorized into the four major themes for colloidal capsule formation, i.e. the Pickering-emulsion based formation of colloidal capsules, the colloidal particle deposition on (sacrificial) templates, the amphiphilicity driven self-assembly of nanoparticle vesicles from polymer-grafted colloids, and the closely related field of nanoparticle membrane-loading of liposomes and polymersomes. The varying fields of colloidal capsule research are then further categorized and discussed for micro- and nano-scaled structures. Finally, a special section is dedicated to colloidal capsules for biological applications, as a diverse range of reports from this field aim at pharmaceutical agent encapsulation, targeted drug-delivery, and theranostics.

  16. Component-Customizable Porous Rare-Earth-Based Colloidal Spheres towards Highly Effective Catalysts and Bioimaging Applications.

    Science.gov (United States)

    Li, Cheng Chao; Rui, Xianhong; Wei, Weifeng; Chen, Libao; Yu, Yan

    2017-11-16

    Multicomponent porous colloidal spheres are of interest because they not only show a combination of the properties associated with all different components, but also usually present synergy effects. However, a combination of different components in a single porous sphere is still greatly challenged due to the different precipitation behaviors of each component. In this work, we have developed a general synthetic route to prepare several categories of porous monodisperse rare-earth (RE)-based colloidal spheres with customizable elemental compositions and a uniform element distribution. The two-step synthetic strategy is based on the integration of coordination chemistry precipitation of RE ions and a subsequent ion-exchange process, which steers clear of obstacles, such as differences in solubility product constant, that are to be found in traditional co-precipitation methods. Our approach provides a new mixing mechanism to realize homogeneous distribution of each element within the porous spheres. An array of binary, ternary, and even senary RE colloidal porous spheres with diameters of 500 nm to 700 nm has been successfully synthesized. Taking advantage of their good dispersibility, porosity, and customizable components, these porous RE oxide spheres show excellent catalytic activity for the reduction of 4-nitrophenol, and promising application in single-phase multifunctional bioprobes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Experimental and theoretical studies of the colloidal stability of nanoparticles-a general interpretation based on stability maps.

    Science.gov (United States)

    Segets, Doris; Marczak, Renata; Schäfer, Stefan; Paula, Carolin; Gnichwitz, Jan-Frederik; Hirsch, Andreas; Peukert, Wolfgang

    2011-06-28

    The current work addresses the understanding of the stabilization of nanoparticles in suspension. Specifically, we study ZnO in ethanol for which the influence of particle size and reactant ratio as well as surface coverage on colloidal stability in dependence of the purification progress was investigated. The results revealed that the well-known ζ-potential determines not only the colloidal stability but also the surface coverage of acetate groups bound to the particle surface. The acetate groups act as molecular spacers between the nanoparticles and prevent agglomeration. Next to DLVO calculations based on the theory of Derjaguin, Landau, Verwey and Overbeek using a core-shell model we find that the stability is better understood in terms of dimensionless numbers which represent attractive forces as well as electrostatic repulsion, steric effects, transport properties, and particle concentration. Evaluating the colloidal stability in dependence of time by means of UV-vis absorption measurements a stability map for ZnO is derived. From this map it becomes clear that the dimensionless steric contribution to colloidal stability scales with a stability parameter including dimensionless repulsion and attraction as well as particle concentration and diffusivity of the particles according to a power law with an exponent of -0.5. Finally, we show that our approach is valid for other stabilizing molecules like cationic dendrons and is generally applicable for a wide range of other material systems within the limitations of vanishing van der Waals forces in refractive index matched situations, vanishing ζ-potential and systems without a stabilizing shell around the particle surface.

  18. Development of a chemiluminescent ELISA and a colloidal gold-based LFIA for TNT detection.

    Science.gov (United States)

    Girotti, S; Eremin, S; Montoya, A; Moreno, M J; Caputo, P; D'Elia, M; Ripani, L; Romolo, F S; Maiolini, E

    2010-01-01

    To identify the explosive used in a terrorist attack, or to obtain an early sign of environmental pollution it is important to use simple and rapid assays able to detect analytes at low levels, possibly on-site. This is particularly true for TNT (2,4,6-trinitrotoluene), one of the most employed explosives in the 20th century and at the same time, because of its toxicity, a well known pollutant. In this work we describe the development of an indirect competitive ELISA with chemiluminescent detection (CL-ELISA) and of a lateral-flow immunoassay (LFIA) based on colloidal gold nanoparticle labels. A commercially available monoclonal antibody was used and 13 specially synthesized conjugates were tested. We optimized the assay by determining the optimal concentration of monoclonal antibody and conjugates and the influence of various non-specific factors such as: tolerance to organic solvents at different concentrations, the washing and competitive step time, and the cross-reactivity with related compounds. The sensitivity and reproducibility of the CL-ELISA were good (LOD and IC(50) values in the ng mL(-1) range, and CV value about 7%). It has been applied to real samples of various materials involved in a controlled explosion of an "improvised explosive device". Three extraction procedures were tested on these samples, all employing methanol as the solvent. The lateral flow immunoassay (LFIA), developed by using the same immunoreagents, reached a detection limit of 1 microg mL(-1) when tested on the same samples analysed by CL-ELISA.

  19. Experimental and numerical iInvestigations of effects of silica colloids on transport of strontium in saturated sand columns.

    Science.gov (United States)

    Bekhit, Hesham M; Hassan, Ahmed E; Harris-Burr, Rebekah; Papelis, Charalambos

    2006-09-01

    Transport experiments with strontium were conducted using saturated sand columns in the presence and absence of silica colloids, and numerical modeling was performed with modeling results compared to experimental data. The experiments were aimed at testing the hypothesis that under certain chemical conditions colloids act as movement-retarding agents and yield a larger effective retardation factor for the migrating contaminant. Four individual experiments were conducted to identify conditions where the mobility of silica colloids is increased or decreased, and a similar set was conducted for strontium transport in the absence of colloids. Mobility of colloids was found to increase with decreasing ionic strength and increasing pH, with the ionic strength having the more significant impact. The reverse effect was obtained for strontium. Based on these results, two additional experiments were conducted where both colloids and strontium were injected at the column inlet. Results showed that under certain conditions of ionic strength and pH (I = 3.0 x 10(-2) M and pH = 4-5.4) colloids retarded the movement of strontium. The retardation effect was obtained in two experiments under slightly modified conditions, which confirms the role of colloids as retarding agents. Afinite difference numerical model was used to (a) simulate mobile breakthrough curves and compare to experimental data and (b) estimate the model parameters describing cotransport of strontium and colloids. The model accurately predicted arrival time and the overall shape of the breakthrough curves.

  20. Conducting polymer based biomolecular electronic devices

    Indian Academy of Sciences (India)

    Conducting polymers such as polypyrroles, polythiophenes and polyanilines have been projected for applications for a wide range of biomolecular electronic devices such as optical, electronic, drug-delivery, memory and biosensing devices. Our group has been actively working towards the application of conducting ...

  1. Colloidal phytosterols: synthesis, characterization and bioaccessibility

    NARCIS (Netherlands)

    Rossi, L.; Seijen ten Hoorn, J.W.M.; Melnikov, S.M.; Velikov, K.P.

    2010-01-01

    We demonstrate the synthesis of phytosterol colloidal particles using a simple food grade method based on antisolvent precipitation in the presence of a non-ionic surfactant. The resulting colloidal particles have a rod-like shape with some degree of crystallinity. The colloidal dispersions display

  2. Conducting polymer based biomolecular electronic devices

    Indian Academy of Sciences (India)

    Biomolecular electronics is rapidly evolving from physics, chemistry, biology, electronics and information technology. Organic materials such as proteins, pigments and conducting polymers have been considered as alternatives for carrying out the functions that are presently being performed by semiconductor silicon.

  3. Colloidal superballs

    NARCIS (Netherlands)

    Rossi, L.

    2012-01-01

    This thesis is organized in four parts as follows. Part 1 focuses on the synthetic aspects of the colloidal model systems that will be used throughout the work described in this thesis. In Chapter 2 we describe synthetic procedures for the preparation of polycrystalline hematite superballs and

  4. Electrochemical sensors based on polyconjugated conducting polymers

    Energy Technology Data Exchange (ETDEWEB)

    Zotti, G. (Ist. di Polarografia ed Elettrochimica Preparativa, Consiglio Nazionale delle Ricerche, Padua (Italy))

    1992-09-01

    An overview of the applications of polyconjugated conducting polymers to electrochemical sensors is given. Gas sensors, ion sensors, and biosensors (non-enzyme and enzyme sensors) are presented and discussed. The role of the polymer as enzyme host and mediator of charge transfer is particularly emphasized in the light of recent results. (orig.).

  5. Conducting polymer based biomolecular electronic devices

    Indian Academy of Sciences (India)

    Abstract. Biomolecular electronics is rapidly evolving from physics, chemistry, biology, electron- ics and information technology. Organic materials such as proteins, pigments and conducting poly- mers have been considered as alternatives for carrying out the functions that are presently being performed by semiconductor ...

  6. Gas Sensors Based on Conducting Polymers

    Directory of Open Access Journals (Sweden)

    Gaoquan Shi

    2007-03-01

    Full Text Available The gas sensors fabricated by using conducting polymers such as polyaniline (PAni, polypyrrole (PPy and poly (3,4-ethylenedioxythiophene (PEDOT as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

  7. Edible Coating Using a Chitosan-Based Colloid Incorporating Grapefruit Seed Extract for Cherry Tomato Safety and Preservation.

    Science.gov (United States)

    Won, Jin Sung; Lee, Seung Jo; Park, Hyeon Hwa; Song, Kyung Bin; Min, Sea C

    2018-01-01

    Grapefruit seed extract (GSE)-containing chitosan-based coating was developed and applied to cherry tomatoes to protect them from Salmonella invasion and improve their storability. The coating colloids were produced by mixing a chitosan colloid (1% [w/w] chitosan) with GSE at various concentrations (0.5%, 0.7%, 1.0%, and 1.2% [w/w]) using high-shear mixing (10000 rpm, 2 min). Coatings with chitosan colloids containing GSE at 0.0%, 0.5%, 0.7%, and 1.0% (w/w) inactivated Salmonella on cherry tomatoes by 1.0 ± 0.3, 1.2 ± 0.3, 1.6 ± 0.1, and 2.0 ± 0.3 log CFU/cherry tomato, respectively. Coatings both with and without GSE (1.0%) effectively inhibited the growth of Salmonella and total mesophilic aerobes, reduced CO 2 generation, and retarded titratable acidity decrease during storage at 10 and 25 °C. The advantage of incorporating GSE in the formulation was demonstrated by delayed microorganism growth and reduced weight loss at 25 °C. The chitosan-GSE coating did not affect lycopene concentration, color, and sensory properties (P > 0.05). Chitosan-GSE coating shows potential for improving the microbiological safety and storability of cherry tomatoes, with stronger efficacy at 25 °C than that of chitosan coating without GSE. A novel chitosan coating containing grape fruit seed extract (GSE) improved the microbiological safety against Salmonella and storability of cherry tomatoes without altering their flavor, demonstrating its strong potential as an effective postharvest technology. Chitosan coating containing GSE might be preferable over chitosan coating without GSE for application to tomatoes that are stored at room temperature in that it more effectively inhibits microbial growth and weight loss than the coating without GSE at 25 °C. © 2017 Institute of Food Technologists®.

  8. Colloid properties in groundwaters from crystalline formations

    International Nuclear Information System (INIS)

    Degueldre, C.A.

    1994-09-01

    Colloids are present in all groundwaters. The role they may play in the migration of safety-relevant radionuclides in the geosphere therefore must be studied. Colloid sampling and characterisation campaigns have been carried out in Switzerland. On the bases of the results from studies in the Grimsel area, Northern Switzerland and the Black Forest, as well as those obtained by other groups concerned with crystalline waters, a consistent picture is emerging. The groundwater colloids in crystalline formations are predominantly comprised of phyllosilicates and silica originating from the aquifer rock. Under constant hydrogeochemical conditions, the colloid concentration is not expected to exceed 100 ng.ml -1 when the calcium concentration is greater than 10 -4 . However, under transient chemical or physical conditions, such as geothermal or tectonic activity, colloid generation may be enhanced and the colloid concentration may reach 10 μg.ml -1 or more, if both the calcium and sodium concentrations are low. In the Nagra Crystalline Reference Water the expected colloid concentration is -1 . This can be compared, for example, to a colloid concentration of about 10 ng.ml -1 found in Zurzach water. The small colloid concentration in the reference water is a consequence of an attachment factor for clay colloids (monmorillonite) close to 1. A model indicates that at pH 8, the nuclide partition coefficients between water and colloid (K p ) must be smaller than 10 7 ml.g -1 if sorption takes place by surface complexation on colloids, = AIOH active groups forming the dominant sorption sites. This pragmatic model is based on the competition between the formation of nuclide hydroxo complexes in solution and their sorption on colloids. Experimental nuclide sorption data on colloids are compared with those obtained by applying this model. For a low colloid concentration, a sorption capacity of the order of 10 -9 M and reversible surface complexation, their presence in the

  9. Proton conduction based on intracrystalline chemical reaction

    International Nuclear Information System (INIS)

    Schuck, G.; Lechner, R.E.; Langer, K.

    2002-01-01

    Proton conductivity in M 3 H(SeO 4 ) 2 crystals (M=K, Rb, Cs) is shown to be due to a dynamic disorder in the form of an intracrystalline chemical equilibrium reaction: alternation between the association of the monomers [HSeO 4 ] 1- and [SeO 4 ] 2- resulting in the dimer [H(SeO 4 ) 2 ] 3- (H-bond formation) and the dissociation of the latter into the two monomers (H-bond breaking). By a combination of quasielastic neutron scattering and FTIR spectroscopy, reaction rates were obtained, as well as rates of proton exchange between selenate ions, leading to diffusion. The results demonstrate that this reaction plays a central role in the mechanism of proton transport in these solid-state protonic conductors. (orig.)

  10. Numerical Analysis of Colloid Transport in Volcanic Ash Soil

    Science.gov (United States)

    Saito, H.; Kawamoto, K.; Komatsu, T.; Moldrup, P.; Simunek, J.

    2006-12-01

    Many studies have been conducted to investigate colloid-facilitated transport of organic or inorganic contaminants in soils. Because many contaminants, even non-soluble contaminants, can sorb onto colloids, failure to account for colloid-facilitated transport may lead to significant errors in predicting movement of contaminants in soils. Volcanic ash soils usually contain a considerable amount of soil particles smaller than 1 micrometer that are considered to have colloidal properties. This study investigated experimentally and numerically the transport of such colloidal particles in a volcanic ash soil called Tachikawa loam under simulated rainfall conditions. Disturbed soil columns were irrigated by controlled rainfall events using artificial rain water (ARW) and colloid solution extracted from Tachikawa loam soil (soil particles smaller than 1 micrometer). There was a continuous leaching of natural colloids with an initial increase in concentrations followed by a long tailing even when irrigated only by ARW. When colloid solution was applied, the breakthrough curve of the applied colloid showed no tailing and least time lag. HYDRUS-1D was used to obtain transport parameters of natural and applied colloids from breakthrough curves using a standard colloid transport model with the first-order deposition and entrainment coefficients (i.e., attachment and detachment terms) to account for kinetic sorption. The estimated distribution coefficient of natural colloids was an order of magnitude larger than that of applied colloids. While the estimated attachment coefficient of natural colloids was negligible, that of applied colloids led to a high retention of applied colloids in soils. The estimated detachment coefficient of natural colloids was three to four orders of magnitude greater than that of applied colloids. One possible explanation is that the estimated attachment coefficient for applied colloids may account for so-called straining that is a physical filtration

  11. Colloidal gas aphron foams: A novel approach to a hydrogel based tissue engineered myocardial patch

    Science.gov (United States)

    Johnson, Elizabeth Edna

    Cardiovascular disease currently affects an estimated 58 million Americans and is the leading cause of death in the US. Over 2.3 million Americans are currently living with heart failure a leading cause of which is acute myocardial infarction, during which a part of the heart muscle is damaged beyond repair. There is a great need to develop treatments for damaged heart tissue. One potential therapy involves replacement of nonfunctioning scar tissue with a patch of healthy, functioning tissue. A tissue engineered cardiac patch would be ideal for such an application. Tissue engineering techniques require the use of porous scaffolds, which serve as a 3-D template for initial cell attachment and grow-th leading to tissue formation. The scaffold must also have mechanical properties closely matching those of the tissues at the site of implantation. Our research presents a new approach to meet these design requirements. A unique interaction between poly(vinyl alcohol) and amino acids has been discovered by our lab, resulting in the production of novel gels. These unique synthetic hydrogels along with one natural hydrogel, alginate (derived from brown seaweed), have been coupled with a new approach to tissue scaffold fabrication using solid colloidal gas aphrons (CGAs). CGAs are colloidal foams containing uniform bubbles with diameters on the order of micrometers. Upon solidification the GCAs form a porous, 3-D network suitable for a tissue scaffold. The project encompasses four specific aims: (I) characterize hydrogel formation mechanism, (II) use colloidal gas aphrons to produce hydrogel scaffolds, (III) chemically and physically characterize scaffold materials and (IV) optimize and evaluate scaffold biocompatibility.

  12. Reinforcement of Conducting Silver-based Materials

    Directory of Open Access Journals (Sweden)

    Heike JUNG

    2014-09-01

    Full Text Available Silver is a well-known material in the field of contact materials because of its high electrical and thermal conductivity. However, due to its bad mechanical and switching properties, silver alloys or reinforcements of the ductile silver matrix are required. Different reinforcements, e. g. tungsten, tungsten carbide, nickel, cadmium oxide or tin oxide, are used in different sectors of switches. To reach an optimal distribution of these reinforcements, various manufacturing techniques (e. g. powder blending, preform infiltration, wet-chemical methods, internal oxidation are being used for the production of these contact materials. Each of these manufacturing routes offers different advantages and disadvantages. The mechanical alloying process displays a successful and efficient method to produce particle-reinforced metal-matrix composite powders. This contribution presents the obtained fine disperse microstructure of tungsten-particle-reinforced silver composite powders produced by the mechanical alloying process and displays this technique as possible route to provide feedstock powders for subsequent consolidation processes. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4889

  13. Interface Recombination in Depleted Heterojunction Photovoltaics based on Colloidal Quantum Dots

    KAUST Repository

    Kemp, Kyle W.

    2013-03-26

    Interface recombination was studied in colloidal quantum dot photovoltaics. Optimization of the TiO2 -PbS interface culminated in the introduction of a thin ZnO buffer layer deposited with atomic layer deposition. Transient photovoltage measurements indicated a nearly two-fold decrease in the recombination rate around 1 sun operating conditions. Improvement to the recombination rate led to a device architecture with superior open circuit voltage (VOC) and photocurrent extraction. Overall a 10% improvement in device efficiency was achieved with Voc enhancements up to 50 mV being realized. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Colloid characterization and quantification in groundwater samples

    Energy Technology Data Exchange (ETDEWEB)

    K. Stephen Kung

    2000-06-01

    This report describes the work conducted at Los Alamos National Laboratory for studying the groundwater colloids for the Yucca Mountain Project in conjunction with the Hydrologic Resources Management Program (HRMP) and the Underground Test Area (UGTA) Project. Colloidal particle size distributions and total particle concentration in groundwater samples are quantified and characterized. Colloid materials from cavity waters collected near underground nuclear explosion sites by HRMP field sampling personnel at the Nevada Test Site (NTS) were quantified. Selected colloid samples were further characterized by electron microscope to evaluate the colloid shapes, elemental compositions, and mineral phases. The authors have evaluated the colloid size and concentration in the natural groundwater sample that was collected from the ER-20-5 well and stored in a 50-gallon (about 200-liter) barrel for several months. This groundwater sample was studied because HRMP personnel have identified trace levels of radionuclides in the water sample. Colloid results show that even though the water sample had filtered through a series of Millipore filters, high-colloid concentrations were identified in all unfiltered and filtered samples. They had studied the samples that were diluted with distilled water and found that diluted samples contained more colloids than the undiluted ones. These results imply that colloids are probably not stable during the storage conditions. Furthermore, results demonstrate that undesired colloids have been introduced into the samples during the storage, filtration, and dilution processes. They have evaluated possible sources of colloid contamination associated with sample collection, filtrating, storage, and analyses of natural groundwaters. The effects of container types and sample storage time on colloid size distribution and total concentration were studied to evaluate colloid stability by using J13 groundwater. The data suggests that groundwater samples

  15. Novel high relaxivity colloidal particles based on the specific phase organisation of amphiphilic gadolinium chelates with cholesterol.

    Science.gov (United States)

    Gløgård, Christian; Stensrud, Gry; Klaveness, Jo

    2003-03-06

    To obtain high T(1)-relaxivity colloidal particles with a simultaneously high loading of amphiphilic Gd-chelates, a novel drug dosage form based on the phase organisation of amphiphilic gadolinium chelates with cholesterol was developed. In order to find a formulation, which exhibit both high T(1)-relaxivity and gives small particles a D-optimal mixture design (experimental design) was applied. Gadolinium 1,4,7-tris(carboxymethyl)-10-(2-hydroxyhexadecyl)-1,4,7,10-tetraazacyclododecane (Gd-HHD-DO3A) and cholesterol at approximately equimolar ratio proved to form thermodynamic stable disc-like colloidal particles as seen by cryo-electron micrographs. T(1)-relaxivity of these particles was typically around 20mM(-1)s(-1) and the size below 100 nm (photon correlation spectroscopy (PCS)). The particles do most probably not interact with blood components as no change in T(1)-relaxivity was observed when the particles were mixed with whole blood. The particles were stable at room temperature for at least 6 months.

  16. Colloidal Gold Probe-Based Immunochromatographic Strip Assay for the Rapid Detection of Microbial Transglutaminase in Frozen Surimi

    Directory of Open Access Journals (Sweden)

    Daming Fan

    2016-01-01

    Full Text Available Adding microbial transglutaminase (MTGase to frozen surimi to enable the surimi to be sold as a higher-grade product at a higher price defrauds surimi product manufacturers and undercuts legitimate industry prices. Therefore, it is important to develop an accurate method of detecting the presence of MTGase in surimi. In this study, an immunochromatographic strip assay with a colloidal gold antibody probe was successfully developed and used to rapidly and qualitatively detect MTGase in surimi samples. The results were obtained in less than 10 min. The limit for the qualitative detection of MTGase using the immunochromatographic strip assay was identified as 1.0 μg/mL. The results of the immunochromatographic strip analysis of frozen surimi samples were verified by comparison with the results of a sandwich enzyme-linked immunosorbent assay. The colloidal gold probe-based immunochromatographic strip assay was thus found to be a rapid, economical, and user friendly method of detecting MTGase in surimi.

  17. How Size Determines the Value of Gold: Economic Aspects of Wet Chemical and Laser-Based Metal Colloid Synthesis.

    Science.gov (United States)

    Jendrzej, Sandra; Gökce, Bilal; Epple, Matthias; Barcikowski, Stephan

    2017-05-05

    Gold is one of the most valuable materials, and its monetary value is enhanced by size reduction from bullions to colloidal nanoparticles by a factor of 450. Wet-chemical reduction with subsequent centrifugation and pulsed laser ablation in liquids are frequently used for pure colloidal gold synthesis. Both methods provide similar physicochemical nanoparticle properties, but are very different synthesis techniques. However, the costs inherent to these methods are surprisingly seldom discussed. Both methods have in common that the labor effort poses the majority of synthesis costs. Besides an increase in batch size and mass concentration, especially an increase of the nanoparticle productivity via higher laser power and centrifugation capacity reduces synthesis costs if pilot- or industrial-scale applications are intended. In this case, laser-based synthesis is more economical if its productivity exceeds a break-even value of 550 mg h -1 , where the costs arising are limited by the metal costs. In contrast to industrial scale production, wet-chemical synthesis is more feasible for laboratory-scale applications, especially if the advantageous nanoparticle properties provided by laser ablation in liquids are not needed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A new class of tunable hypersonic phononic crystals based on polymer-tethered colloids.

    Science.gov (United States)

    Alonso-Redondo, E; Schmitt, M; Urbach, Z; Hui, C M; Sainidou, R; Rembert, P; Matyjaszewski, K; Bockstaller, M R; Fytas, G

    2015-09-22

    The design and engineering of hybrid materials exhibiting tailored phononic band gaps are fundamentally relevant to innovative material technologies in areas ranging from acoustics to thermo-optic devices. Phononic hybridization gaps, originating from the anti-crossing between local resonant and propagating modes, have attracted particular interest because of their relative robustness to structural disorder and the associated benefit to 'manufacturability'. Although hybridization gap materials are well known, their economic fabrication and efficient control of the gap frequency have remained elusive because of the limited property variability and expensive fabrication methodologies. Here we report a new strategy to realize hybridization gap materials by harnessing the 'anisotropic elasticity' across the particle-polymer interface in densely polymer-tethered colloidal particles. Theoretical and Brillouin scattering analysis confirm both the robustness to disorder and the tunability of the resulting hybridization gap and provide guidelines for the economic synthesis of new materials with deliberately controlled gap position and width frequencies.

  19. High efficiency silicon nanodisk laser based on colloidal CdSe/ZnS QDs

    Directory of Open Access Journals (Sweden)

    Min-Hsiung Shih

    2011-07-01

    Full Text Available Using colloidal CdSe/ZnS quantum dots in the submicron-sized silicon disk cavity, we have developed a visible wavelength nanodisk laser that operates under extremely low threshold power at room temperature. Time-resolved photoluminescence (PL of QDs; nanodisk by e-beam lithography. Observation of lasing action at 594 nm wavelength for quantum dots on a nanodisk (750 nm in diameter cavity and an ultra-low threshold of 2.8 µW. From QD concentration dependence studies we achieved nearly sevenfold increase in spontaneous emission (SE rate. We have achieved high efficient and high SE coupling rate in such a QD nanodisk laser.

  20. Structure based descriptors for the estimation of colloidal interactions and protein aggregation propensities.

    Directory of Open Access Journals (Sweden)

    Michael Brunsteiner

    Full Text Available The control of protein aggregation is an important requirement in the development of bio-pharmaceutical formulations. Here a simple protein model is proposed that was used in molecular dynamics simulations to obtain a quantitative assessment of the relative contributions of proteins' net-charges, dipole-moments, and the size of hydrophobic or charged surface patches to their colloidal interactions. The results demonstrate that the strength of these interactions correlate with net-charge and dipole moment. Variation of both these descriptors within ranges typical for globular proteins have a comparable effect. By comparison no clear trends can be observed upon varying the size of hydrophobic or charged patches while keeping the other parameters constant. The results are discussed in the context of experimental literature data on protein aggregation. They provide a clear guide line for the development of improved algorithms for the prediction of aggregation propensities.

  1. Nanoparticle metrology standards based on the time-resolved fluorescence anisotropy of silica colloids

    Science.gov (United States)

    Apperson, Kathleen; Karolin, Jan; Martin, Robert W.; Birch, David J. S.

    2009-02-01

    We demonstrate nanoparticle size measurement using time-resolved fluorescence anisotropy decay in relation to establishing a nanometrology standard. The rotational correlation time equivalent to the isotropic Brownian rotation of a fluorescent 6-methoxyquinolinium dye attached to amorphous silica nanoparticles was determined in three different LUDOXLUDOX is a registered trademark of DuPont Corporation. colloids from the complex fluorescence anisotropy decay observed. Once competing depolarization and nanoparticle aggregation had been taken into account, good agreement was found of 4.0 ± 0.4 nm, 6.4 ± 0.5 nm and 11.0 ± 1.6 nm corresponding to the manufacturer's reported particle radii of 3.5 nm, 6 nm and 11 nm, for LUDOX SM30, AM30 and AS40 respectively. We describe the measurement science required for acquisition and interpretation of fluorescence anisotropy decay data in order to determine nanoparticle size while highlighting the limitations and useful range of measurement.

  2. Nanoparticle metrology standards based on the time-resolved fluorescence anisotropy of silica colloids

    International Nuclear Information System (INIS)

    Apperson, Kathleen; Karolin, Jan; Martin, Robert W; Birch, David J S

    2009-01-01

    We demonstrate nanoparticle size measurement using time-resolved fluorescence anisotropy decay in relation to establishing a nanometrology standard. The rotational correlation time equivalent to the isotropic Brownian rotation of a fluorescent 6-methoxyquinolinium dye attached to amorphous silica nanoparticles was determined in three different LUDOX colloids from the complex fluorescence anisotropy decay observed. Once competing depolarization and nanoparticle aggregation had been taken into account, good agreement was found of 4.0 ± 0.4 nm, 6.4 ± 0.5 nm and 11.0 ± 1.6 nm corresponding to the manufacturer's reported particle radii of 3.5 nm, 6 nm and 11 nm, for LUDOX SM30, AM30 and AS40 respectively. We describe the measurement science required for acquisition and interpretation of fluorescence anisotropy decay data in order to determine nanoparticle size while highlighting the limitations and useful range of measurement

  3. Infrared Harvesting Colloidal Quantum Dot Solar Cell Based on Multi-scale Disordered Electrodes

    KAUST Repository

    Tian, Yi

    2015-06-23

    Colloidal quantum dot photovoltaics (CQDPV) offer a big potential to be a renewable energy source due to low cost and tunable band-gap. Currently, the certified power conversion efficiency of CQDPV has reached 9.2%. Compared to the 31% theoretical efficiency limit of single junction solar cells, device performances have still have a large potential to be improved. For photovoltaic devices, a classical way to enhance absorption is to increase the thickness of the active layers. Although this approach can improve absorption, it reduces the charge carriers extraction efficiency. Photo-generated carriers, in fact, are prone to recombine within the defects inside CQD active layers. In an effort to solve this problem, we proposed to increase light absorption from a given thickness of colloidal quantum dot layers with the assistance of disorder. Our approach is to develop new types of electrodes with multi-scale disordered features, which localize energy into the active layer through plasmonic effects. We fabricated nanostructured gold substrates by electrochemical methods, which allow to control surface disorder as a function of deposition conditions. We demonstrated that the light absorption from 600 nm to 800 nm is impressively enhanced, when the disorder of the nanostructured surface increases. Compared to the planar case, the most disorder case increased 65% light absorption at the wavelength of λ = 700nm in the 100 nm PbS film. The average absorption enhancement across visible and infrared region in 100 nm PbS film is 49.94%. By developing a photovoltaic module, we measured a dramatic 34% improvement in the short-circuit current density of the device. The power conversion efficiency of the tested device in top-illumination configuration showed 25% enhancement.

  4. Coupled effect of extended DLVO and capillary interactions on the retention and transport of colloids through unsaturated porous media.

    Science.gov (United States)

    Xu, Shuang; Qi, Jun; Chen, Xijuan; Lazouskaya, Volha; Zhuang, Jie; Jin, Yan

    2016-12-15

    Colloids are potential vectors of contaminants in the subsurface environment. The knowledge of transport and retention behaviors of colloids is of primary importance for assessment and prediction of subsurface pollution risks. In this study, sand column experiments were conducted to investigate the coupled effects of various interfacial forces on the retention and transport of a hydrophilic silica colloid and a relatively hydrophobic latex colloid. Water column experiments were performed to observe the movement of colloids with air bubbles. Extended DLVO interaction energies and capillary potential energy were calculated to analyze colloid retention at air-water interface (AWI), solid-water interface (SWI), and air-water-solid interface (AWS). Results show that colloid retention decreases due to increase in electrostatic repulsion and Born repulsion as well as decrease in Lewis acid-base attraction and hydrophobic interactions. Water content effect and hydrophobic effect on colloid retention become more predominant in the solution of higher ionic strength. Colloid retention at AWI is minimal (i.e., due to nonexistence of primary and secondary minima) at the ionic strengths colloids is 4-5 orders of magnitude greater than the extended DLVO interaction energy (~10 3 K B T), suggesting that capillary retention at AWS is the primary mechanism controlling colloid retention in unsaturated porous media. Results from this study show that immobile solid phase (e.g., soil) could be much more important than air phase in determining colloid retention in unsaturated porous media under unfavorable conditions, especially in the solutions of high ionic strengths. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Colloid-based multiplexed method for screening plant biomass-degrading glycoside hydrolase activities in microbial communities

    Energy Technology Data Exchange (ETDEWEB)

    Reindl, W.; Deng, K.; Gladden, J.M.; Cheng, G.; Wong, A.; Singer, S.W.; Singh, S.; Lee, J.-C.; Yao, J.-S.; Hazen, T.C.; Singh, A.K; Simmons, B.A.; Adams, P.D.; Northen, T.R.

    2011-05-01

    The enzymatic hydrolysis of long-chain polysaccharides is a crucial step in the conversion of biomass to lignocellulosic biofuels. The identification and characterization of optimal glycoside hydrolases is dependent on enzyme activity assays, however existing methods are limited in terms of compatibility with a broad range of reaction conditions, sample complexity, and especially multiplexity. The method we present is a multiplexed approach based on Nanostructure-Initiator Mass Spectrometry (NIMS) that allowed studying several glycolytic activities in parallel under diverse assay conditions. Although the substrate analogs carried a highly hydrophobic perfluorinated tag, assays could be performed in aqueous solutions due colloid formation of the substrate molecules. We first validated our method by analyzing known {beta}-glucosidase and {beta}-xylosidase activities in single and parallel assay setups, followed by the identification and characterization of yet unknown glycoside hydrolase activities in microbial communities.

  6. Anisotropic Model Colloids

    NARCIS (Netherlands)

    van Kats, C.M.

    2008-01-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are

  7. EDITORIAL: Colloidal suspensions Colloidal suspensions

    Science.gov (United States)

    Petukhov, Andrei; Kegel, Willem; van Duijneveldt, Jeroen

    2011-05-01

    Special issue in honour of Henk Lekkerkerker's 65th birthday Professor Henk N W Lekkerkerker is a world-leading authority in the field of experimental and theoretical soft condensed matter. On the occasion of his 65th birthday in the summer of 2011, this special issue celebrates his many contributions to science. Henk Lekkerkerker obtained his undergraduate degree in chemistry at the University of Utrecht (1968) and moved to Calgary where he received his PhD in 1971. He moved to Brussels as a NATO fellow at the Université Libre de Bruxelles and was appointed to an assistant professorship (1974), an associate professorship (1977) and a full professorship (1980) in physical chemistry at the Vrije Universiteit Brussel. In 1985 he returned to The Netherlands to take up a professorship at the Van 't Hoff Laboratory, where he has been ever since. He has received a series of awards during his career, including the Onsager Medal (1999) of the University of Trondheim, the Bakhuys Roozeboom Gold Medal (2003) of the Royal Dutch Academy of Arts and Sciences (KNAW), the ECIS-Rhodia European Colloid and Interface Prize (2003), and the Liquid Matter Prize of the European Physical Society (2008). He was elected a member of KNAW in 1996, was awarded an Academy Chair position in 2005, and has held several visiting lectureships. Henk's work focuses on phase transitions in soft condensed matter, and he has made seminal contributions to both the theoretical and experimental aspects of this field. Here we highlight three major themes running through his work, and a few selected publications. So-called depletion interactions may lead to phase separation in colloid-polymer mixtures, and Henk realised that the partitioning of polymer needs to be taken into account to describe the phase behaviour correctly [1]. Colloidal suspensions can be used as model fluids, with the time- and length-scales involved leading to novel opportunities, notably the direct observation of capillary waves at a

  8. On conduction mechanism in paramagnetic phase of Gd based ...

    Indian Academy of Sciences (India)

    ble mechanism for conduction in Gd based manganites. The conduction mechanism in the paramagnetic phase is a matter of controversy as different schools of thought propose diffe- rent models for conduction. For example, data on certain com- pounds were fitted with purely activated law (Kusters et al. 1989; Hundley et al ...

  9. Direct Visualization of Conformation and Dense Packing of DNA-Based Soft Colloids

    Science.gov (United States)

    Zhang, Jing; Lettinga, Paul M.; Dhont, Jan K. G.; Stiakakis, Emmanuel

    2014-12-01

    Soft colloids—such as polymer-coated particles, star polymers, block-copolymer micelles, microgels—constitute a broad class of materials where microscopic properties such as deformability and penetrability of the particle play a key role in tailoring their macroscopic properties which is of interest in many technological areas. The ability to access these microscopic properties is not yet demonstrated despite its great importance. Here we introduce novel DNA-coated colloids with star-shaped architecture that allows accessing the above local structural information by directly visualizing their intramolecular monomer density profile and arm's free-end locations with confocal fluorescent microscopy. Compression experiments on a two-dimensional hexagonal lattice formed by these macromolecular assemblies reveal an exceptional resistance to mutual interpenetration of their charged corona at pressures approaching the MPa range. Furthermore, we find that this lattice, in a close packing configuration, is surprisingly tolerant to particle size variation. We anticipate that these stimuli-responsive materials could aid to get deeper insight in a wide range of problems in soft matter, including the study and design of biomimetic lubricated surfaces.

  10. Preparation of SMART wound dressings based on colloidal microgels and textile fibres

    Science.gov (United States)

    Cornelius, Victoria J.; Majcen, Natasa; Snowden, Martin J.; Mitchell, John C.; Voncina, Bojana

    2007-01-01

    Wound dressings and other types of wound healing technologies are experiencing fast-paced development and rapid growth. As the population ages, demand will continue to rise for advanced dressings used to treat chronic wounds, such as pressure ulcers, venous stasis ulcers, and diabetic ulcers. Moist wound dressings, which facilitate natural wound healing in a cost-effective manner, will be increasingly important. In commercially available hydrogel / gauze wound dressings the gel swells to adsorb wound excreta and provide an efficient non adhesive particle barrier. An alternative to hydrogels are microgels. Essentially discrete colloidal gel particles, as a result of their very high surface area to volume ratio compared to bulk gels, they have a much faster response to external stimuli such as temperature or pH. In response to either an increase or decrease in solvent quality these porous networks shrink and swell reversibly. When swollen the interstitial regions within the polymer matrix are available for further chemistry; such as the incorporation of small molecules. The reversible shrinking and swelling as a function of external stimuli provides a novel drug release system. As the environmental conditions of a wound change over its lifetime, tending to increase in pH if there is an infection combining these discrete polymeric particles with a substrate such as cotton, results in a smart wound dressing.

  11. Silica nanoparticle-based dual imaging colloidal hybrids: cancer cell imaging and biodistribution

    Directory of Open Access Journals (Sweden)

    Lee H

    2015-08-01

    Full Text Available Haisung Lee,1 Dongkyung Sung,2 Jinhoon Kim,3 Byung-Tae Kim,3 Tuntun Wang,4 Seong Soo A An,5 Soo-Won Seo,6 Dong Kee Yi4 1Molecular Diagnostics, In Vitro Diagnostics Unit, New Business Division, SK Telecom, 2Department of Life Sciences, Graduate School of Korea University, 3Interdisciplinary Graduate Program of Biomedical Engineering, School of Medicine, Sungkyunkwan University, Samsung Medical Center, 4Department of Chemistry, Myongji University, Seoul, 5Department of Bionanotechnology, Gachon Medical Research Institute, Gachon University, Seongnam, 6Medical Device Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Republic of Korea Abstract: In this study, fluorescent dye-conjugated magnetic resonance (MR imaging agents were investigated in T mode. Gadolinium-conjugated silica nanoparticles were successfully synthesized for both MR imaging and fluorescence diagnostics. Polyamine and polycarboxyl functional groups were modified chemically on the surface of the silica nanoparticles for efficient conjugation of gadolinium ions. The derived gadolinium-conjugated silica nanoparticles were investigated by zeta potential analysis, transmission electron microscopy, inductively coupled plasma mass spectrometry, and energy dispersive x-ray spectroscopy. MR equipment was used to investigate their use as contrast-enhancing agents in T1 mode under a 9.4 T magnetic field. In addition, we tracked the distribution of the gadolinium-conjugated nanoparticles in both lung cancer cells and organs in mice. Keywords: dual bioimaging, MR imaging, silica colloid, T1 contrast imaging, nanohybrid

  12. High-Power Genuine Ultraviolet Light-Emitting Diodes Based On Colloidal Nanocrystal Quantum Dots.

    Science.gov (United States)

    Kwak, Jeonghun; Lim, Jaehoon; Park, Myeongjin; Lee, Seonghoon; Char, Kookheon; Lee, Changhee

    2015-06-10

    Thin-film ultraviolet (UV) light-emitting diodes (LEDs) with emission wavelengths below 400 nm are emerging as promising light sources for various purposes, from our daily lives to industrial applications. However, current thin-film UV-emitting devices radiate not only UV light but also visible light. Here, we introduce genuine UV-emitting colloidal nanocrystal quantum dot (NQD) LEDs (QLEDs) using precisely controlled NQDs consisting of a 2.5-nm-sized CdZnS ternary core and a ZnS shell. The effective core size is further reduced during the shell growth via the atomic diffusion of interior Cd atoms to the exterior ZnS shell, compensating for the photoluminescence red shift. This design enables us to develop CdZnS@ZnS UV QLEDs with pure UV emission and minimal parasitic peaks. The irradiance is as high as 2.0-13.9 mW cm(-2) at the peak wavelengths of 377-390 nm, several orders of magnitude higher than that of other thin-film UV LEDs.

  13. Electrical conduction in solid materials physicochemical bases and possible applications

    CERN Document Server

    Suchet, J P

    2013-01-01

    Electrical Conduction in Solid Materials (Physicochemical Bases and Possible Applications) investigates the physicochemical bases and possible applications of electrical conduction in solid materials, with emphasis on conductors, semiconductors, and insulators. Topics range from the interatomic bonds of conductors to the effective atomic charge in conventional semiconductors and magnetic transitions in switching semiconductors. Comprised of 10 chapters, this volume begins with a description of electrical conduction in conductors and semiconductors, metals and alloys, as well as interatomic bon

  14. Training Residential Staff to Conduct Trial-Based Functional Analyses

    Science.gov (United States)

    Lambert, Joseph M.; Bloom, Sarah E.; Kunnavatana, S. Shanun; Collins, Shawnee D.; Clay, Casey J.

    2013-01-01

    We taught 6 supervisors of a residential service provider for adults with developmental disabilities to train 9 house managers to conduct trial-based functional analyses. Effects of the training were evaluated with a nonconcurrent multiple baseline. Results suggest that house managers can be trained to conduct trial-based functional analyses with…

  15. Colloid transport in saturated porous media: Elimination of attachment efficiency in a new colloid transport model

    Science.gov (United States)

    Landkamer, Lee L.; Harvey, Ronald W.; Scheibe, Timothy D.; Ryan, Joseph N.

    2013-01-01

    A colloid transport model is introduced that is conceptually simple yet captures the essential features of colloid transport and retention in saturated porous media when colloid retention is dominated by the secondary minimum because an electrostatic barrier inhibits substantial deposition in the primary minimum. This model is based on conventional colloid filtration theory (CFT) but eliminates the empirical concept of attachment efficiency. The colloid deposition rate is computed directly from CFT by assuming all predicted interceptions of colloids by collectors result in at least temporary deposition in the secondary minimum. Also, a new paradigm for colloid re-entrainment based on colloid population heterogeneity is introduced. To accomplish this, the initial colloid population is divided into two fractions. One fraction, by virtue of physiochemical characteristics (e.g., size and charge), will always be re-entrained after capture in a secondary minimum. The remaining fraction of colloids, again as a result of physiochemical characteristics, will be retained “irreversibly” when captured by a secondary minimum. Assuming the dispersion coefficient can be estimated from tracer behavior, this model has only two fitting parameters: (1) the fraction of the initial colloid population that will be retained “irreversibly” upon interception by a secondary minimum, and (2) the rate at which reversibly retained colloids leave the secondary minimum. These two parameters were correlated to the depth of the Derjaguin-Landau-Verwey-Overbeek (DLVO) secondary energy minimum and pore-water velocity, two physical forces that influence colloid transport. Given this correlation, the model serves as a heuristic tool for exploring the influence of physical parameters such as surface potential and fluid velocity on colloid transport.

  16. Synchrotron radiation based multi-scale structural characterization of CoPt{sub 3} colloidal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zargham, Ardalan

    2010-08-05

    Bimetallic CoPt{sub 3} nanoparticles represent a category of colloidal nanoparticles with high application potentials in, e.g., heterogeneous catalysis, sensor technology, and magnetic storage media. Deposition of this system on functionalized supports delivers opportunities for controlled immobilization of the nanoparticles. In this work, self-assembled monolayers (SAMs) of n-alkanethiol molecules served as functionalizing material for the Au covered Si substrates. Deposition of the ligand-terminated nanoparticles took place by means of spin and dip coating and has been optimized for each of the mentioned methods so that monolayers of nanoparticles on supports were fabricated with a well-controlled coverage The morphology of the nanoparticle film arranged is addressed by grazing-incidence small angle x-ray scattering (GISAXS). This together with x-ray standing waves in total external reflection (TER-XSW) enables a 3D structural characterization of such nanoparticle films, so that the mean particle size, mean distance of the arranged nanoparticle films to the substrate, as well as the mean particle-particle distance in lateral direction have been determined. TER-XSW, being an element-specific position-sensitive method, also reveals the elemental distribution of the particles which complementary provides a fundamental understanding of their internal structure. The CoPt{sub 3} nanoparticles investigated here exhibit a core-shell-like structure with cores of CoPt{sub 3} and shells mainly comprise Co. The results regarding the internal structure of the nanoparticles were then verified by extended X-ray absorption fine structure (EXAFS) measurements. (orig.)

  17. Nonequilibrium forces between dragged ultrasoft colloids.

    Science.gov (United States)

    Singh, Sunil P; Winkler, Roland G; Gompper, Gerhard

    2011-10-07

    The dynamical deformation of ultrasoft colloids as well as their dynamic frictional forces are numerically investigated, when one colloid is dragged past another at constant velocity. Hydrodynamic interactions are captured by a particle-based mesoscopic simulation method. At vanishing relative velocity, the equilibrium repulsive force-distance curve is obtained. At large drag velocities, in contrast, we find an apparent attractive force for departing colloids along the dragging direction. The deformation, in the close encounter of colloids, and the energy dissipation are examined as a function of the drag velocity and their separation.

  18. Effect of particle shape on colloid retention and release in saturated porous media.

    Science.gov (United States)

    Liu, Qiang; Lazouskaya, Volha; He, Qingxiang; Jin, Yan

    2010-01-01

    Colloidal particles of environmental concern often have nonspherical shapes. However, theories and models such as the classical filtration theory have been developed based on the behavior of spherical particles. This study examined the effect of particle shape on colloid retention (e.g., attachment and straining) and release in saturated porous media. Two- and three-step transport experiments were conducted in water-saturated glass bead columns using colloids dispersed in deionized water and an electrolyte solution. The particles used in the experiments were carboxylate-modified latex colloids of spherical (500 nm diam.) and rod (aspect ratio, 7.0) shapes. The rod-like particles were prepared by stretching the spherical particles. Analysis of the colloid breakthrough curves indicates that particle shape affected transport behavior, but retention did not increase with increasing aspect ratio. Retention of the spherical particles occurred mainly in the secondary energy minimum, whereas retention of rod-like particles occurred in primary and secondary energy minima. There was less straining of rod-like particles compared with spherical ones, indicating that the minor axis was the critical dimension controlling the process. Release of spherical particles on elution was instantaneous, whereas release of rod-like particles was rate limited, giving rise to long tails, implying an orientation effect for rod-like colloids. The results suggest that the differences in electrostatic properties and shape contributed to the observed different retention and release behaviors of the two colloids.

  19. Noninvasive quantitative measurement of colloid transport in mesoscale porous media using time lapse fluorescence imaging.

    Science.gov (United States)

    Bridge, Jonathan W; Banwart, Steven A; Heathwaite, A Louise

    2006-10-01

    We demonstrate noninvasive quantitative imaging of colloid and solute transport at millimeter to decimeter (meso-) scale. Ultraviolet (UV) excited fluorescent solute and colloid tracers were independently measured simultaneously during co-advection through saturated quartz sand. Pulse-input experiments were conducted at constant flow rates and ionic strengths 10(-3), 10(-2) and 10(-1) M NaCl. Tracers were 1.9 microm carboxylate latex microspheres and disodium fluorescein. Spatial moments analysis was used to quantify relative changes in mass distribution of the colloid and solute tracers over time. The solute advected through the sand at a constant velocity proportional to flow rate and was described well by a conservative transport model (CXTFIT). In unfavorable deposition conditions increasing ionic strength produced significant reduction in colloid center of mass transport velocity over time. Velocity trends correlated with the increasing fraction of colloid mass retained along the flowpath. Attachment efficiencies (defined by colloid filtration theory) calculated from nondestructive retained mass data were 0.013 +/- 0.03, 0.09 +/- 0.02, and 0.22 +/- 0.05 at 10(-3), 10(-2), and 10(-1) M ionic strength, respectively, which compared well with previously published data from breakthrough curves and destructive sampling. Mesoscale imaging of colloid mass dynamics can quantify key deposition and transport parameters based on noninvasive, nondestructive, spatially high-resolution data.

  20. Sensitivity analyses of a colloid-facilitated contaminant transport model for unsaturated heterogeneous soil conditions.

    Science.gov (United States)

    Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean

    2013-04-01

    effects and the one-at-a-time approach (O.A.T); and (ii), we applied Sobol's global sensitivity analysis method which is based on variance decompositions. Results illustrate that ψm (maximum sorption rate of mobile colloids), kdmc (solute desorption rate from mobile colloids), and Ks (saturated hydraulic conductivity) are the most sensitive parameters with respect to the contaminant travel time. The analyses indicate that this new module is able to simulate the colloid-facilitated contaminant transport. However, validations under laboratory conditions are needed to confirm the occurrence of the colloid transport phenomenon and to understand model prediction under non-saturated soil conditions. Future work will involve monitoring of the colloidal transport phenomenon through soil column experiments. The anticipated outcome will provide valuable information on the understanding of the dominant mechanisms responsible for colloidal transports, colloid-facilitated contaminant transport and, also, the colloid detachment/deposition processes impacts on soil hydraulic properties. References: Šimůnek, J., C. He, L. Pang, & S. A. Bradford, Colloid-Facilitated Solute Transport in Variably Saturated Porous Media: Numerical Model and Experimental Verification, Vadose Zone Journal, 2006, 5, 1035-1047 Šimůnek, J., M. Šejna, & M. Th. van Genuchten, The C-Ride Module for HYDRUS (2D/3D) Simulating Two-Dimensional Colloid-Facilitated Solute Transport in Variably-Saturated Porous Media, Version 1.0, PC Progress, Prague, Czech Republic, 45 pp., 2012.

  1. Graphene metamaterials based tunable terahertz absorber: effective surface conductivity approach

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Lavrinenko, Andrei

    2013-01-01

    In this paper we present the efficient design of functional thin-film metamaterial devices with the effective surface conductivity approach. As an example, we demonstrate a graphene based perfect absorber. After formulating the requirements to the perfect absorber in terms of surface conductivity...... we investigate the properties of graphene wire medium and graphene fishnet metamaterials and demonstrate both narrowband and broadband tunable absorbers.......In this paper we present the efficient design of functional thin-film metamaterial devices with the effective surface conductivity approach. As an example, we demonstrate a graphene based perfect absorber. After formulating the requirements to the perfect absorber in terms of surface conductivity...

  2. Effect of island shape on dielectrophoretic assembly of metal nanoparticle chains in a conductive-island-based microelectrode system

    International Nuclear Information System (INIS)

    Ding, Haitao; Shao, Jinyou; Ding, Yucheng; Liu, Weiyu; Li, Xiangming; Tian, Hongmiao; Zhou, Yaopei

    2015-01-01

    Highlights: • Conductive island shape influences the dynamic process occurring in DEP assembly of 10 nm gold nanoparticles in a conductive-island-based microelectrode system. • The DEP-assembled nanoparticle wires form a straighter conduction path with the increase in the geometric angle of conductive island tip. • The different island shapes distort the DEP force distribution and increase the local electrothermally induced fluid flow to different extents, which is important for the morphology and electrical conductance quality of the DEP-assembled metal nanoparticle chains. - Abstract: The electrical conduction quality of an electric circuit connection formed by dielectrophoretic (DEP)-assembled metal nanoparticle wires between small conductive elements plays a significant role in electronic devices. One of the major challenges for improving the electrical conductance of nanowires is optimizing their geometric morphology. So far, the electrical conduction quality has been enhanced by optimizing the AC frequency and conductivity of nanoparticle suspensions. Herein, the effect of the conductive island shapes on the dynamic process occurring in a DEP assembly of 10 nm gold nanoparticles was investigated in a conductive-island-based microelectrode system. The nanoparticle wires between the microelectrodes were assembled in situ from colloidal suspensions. The wires were grown in a much straighter route by increasing the geometric angle of the conductive-island tip. To validate the experiments, the effects of mutual DEP interactions and electrothermally induced fluid flow on the dynamic behavior of particle motion for different island geometric configurations in the conductive-island-based microelectrode system were determined by numerical simulations. The simulation results are consistent with those of experiments. This indicates that different conductive island shapes change the distribution of DEP force and increase the electrothermally induced fluid flow to

  3. ZnO based transparent conductive oxide films with controlled type of conduction

    Energy Technology Data Exchange (ETDEWEB)

    Zaharescu, M., E-mail: mzaharescu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Mihaiu, S., E-mail: smihaiu@icf.ro [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Toader, A. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Atkinson, I., E-mail: irinaatkinson@yahoo.com [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Calderon-Moreno, J.; Anastasescu, M.; Nicolescu, M.; Duta, M.; Gartner, M. [Institute of Physical Chemistry “Ilie Murgulescu”, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania); Vojisavljevic, K.; Malic, B. [Institute Jožef Stefan, Ljubljana (Slovenia); Ivanov, V.A.; Zaretskaya, E.P. [State Scientific and Production Association “Scientific-Practical Materials Research Center of the National Academy of Science Belarus, P. Brovska str.19, 220072, Minsk (Belarus)

    2014-11-28

    The transparent conductive oxide films with controlled type of conduction are of great importance and their preparation is intensively studied. In our work, the preparation of such films based on doped ZnO was realized in order to achieve controlled type of conduction and high concentration of the charge carriers. Sol–gel method was used for films preparation and several dopants were tested (Sn, Li, Ni). Multilayer deposition was performed on several substrates: SiO{sub 2}/Si wafers, silica-soda-lime and/or silica glasses. The structural and morphological characterization of the obtained films were done by scanning electron microscopy, X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy and atomic force microscopy respectively, while spectroscopic ellipsometry and transmittance measurements were done for determination of optical properties. The selected samples with the best structural, morphological and optical properties were subjected to electrical measurement (Hall and Seebeck effect). In all studied cases, samples with good adherence and homogeneous morphology as well as monophasic wurtzite type structure were obtained. The optical constants (refractive index and extinction coefficient) were calculated from spectroscopic ellipsometry data using Cauchy model. Films with n- or p-type conduction were obtained depending on the composition, number of deposition and thermal treatment temperature. - Highlights: • Transparent conductive ZnO based thin films were prepared by the sol–gel method. • Controlled type of conduction is obtained in (Sn, Li) doped and Li-Ni co-doped ZnO films. • Hall and Seebeck measurements proved the p-type conductivity for Li-Ni co-doped ZnO films. • The p-type conductivity was maintained even after 4-months of storage. • Influence of dopant- and substrate-type on the ZnO films properties was established.

  4. Polymer-embedded colloidal lead-sulfide nanocrystals integrated to vertically slotted silicon-based ring resonators for telecom applications

    Science.gov (United States)

    Humer, Markus; Guider, Romain; Hackl, Florian; Fromherz, Thomas

    2013-01-01

    The main drawback of the rapidly evolving field of silicon photonics lies in the absence of efficient monolithically integrated radiation sources as a consequence of the indirect bandgap of Si and Ge. Relevant alternatives based on the hybrid combination of Si with optically active materials have to be technologically simple, temporally stable, and provide efficient coupling to the Si waveguides. Lead-sulfide nanocrystals (NCs) were blended into a polymer resist suitable for deep-UV- and electron-beam lithography and integrated into Si-based vertically slotted waveguides and ring resonators. The polymer both stabilizes the NC's photoluminescence emission against degradation under ambient conditions and allows lithographic patterning of this compound material. After integration into the optoelectronic structures and upon optical pumping, intense photoluminescence emission from ring resonators was recorded at the output of bus-waveguides. The resonator quality factors were investigated for polymer-NC compounds with NC concentrations in the range between 0.1 and 8 vol%. The spontaneous emission rate enhancement for vertically slotted resonators was estimated to be a factor of two higher as compared to unslotted ones. The stable integration of colloidal NCs as well as the improved light coupling to silicon circuits is an important step in the development of silicon-based hybrid photonics.

  5. Lateral flow test strip based on colloidal selenium immunoassay for rapid detection of melamine in milk, milk powder, and animal feed

    Directory of Open Access Journals (Sweden)

    Wang ZZ

    2014-04-01

    Full Text Available Zhizeng Wang,1 Dejuan Zhi,2 Yang Zhao,1 Hailong Zhang,2 Xin Wang,2 Yi Ru,1 Hongyu Li1,2 1MOE Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, People's Republic of China; 2Institute of Microbiology and Biochemical Pharmacy, School of Pharmaceutics, Lanzhou University, Lanzhou, People's Republic of China Abstract: Although high melamine (MEL intake has been proven to cause serious health problems, MEL is sometimes illegally added to milk products and animal feed, arousing serious food safety concerns. A satisfactory method of detecting MEL in onsite or in-home testing is in urgent need of development. This work aimed to explore a rapid, convenient, and cost-effective method of identifying MEL in milk products or other food by colloidal selenium-based lateral flow immunoassay. Colloidal selenium was synthesized by L-ascorbic acid to reduce seleninic acid at room temperature. After conjugation with a monoclonal antibody anti-MEL, a test strip was successfully prepared. The detection limit of the test strip reached 150 µg/kg, 1,000 µg/kg, and 800 µg/kg in liquid milk, milk powder, and animal feed, respectively. No cross-reactions with homologues cyanuric acid, cyanurodiamide, or ammelide were found. Moreover, the MEL test strip can remain stable after storage for 1 year at room temperature. Our results demonstrate that the colloidal selenium MEL test strip can detect MEL in adulterated milk products or animal feed conveniently, rapidly, and sensitively. In contrast with a colloidal gold MEL test strip, the colloidal selenium MEL test strip was easy to prepare and more cost-efficient. Keywords: melamine, selenium nanoparticles, test strip, milk, animal feed, dairy food

  6. Enabling Flexible Heterostructures for Li-Ion Battery Anodes Based on Nanotube and Liquid-Phase Exfoliated 2D Gallium Chalcogenide Nanosheet Colloidal Solutions.

    Science.gov (United States)

    Zhang, Chuanfang John; Park, Sang-Hoon; Ronan, Oskar; Harvey, Andrew; Seral-Ascaso, Andrés; Lin, Zifeng; McEvoy, Niall; Boland, Conor S; Berner, Nina C; Duesberg, Georg S; Rozier, Patrick; Coleman, Jonathan N; Nicolosi, Valeria

    2017-09-01

    2D metal chalcogenide (MC) nanosheets (NS) have displayed high capacities as lithium-ion battery (LiB) anodes. Nevertheless, their complicated synthesis routes coupled with low electronic conductivity greatly limit them as promising LiB electrode material. Here, this work reports a facile single-walled carbon nanotube (SWCNT) percolating strategy for efficiently maximizing the electrochemical performances of gallium chalcogenide (GaX, X = S or Se). Multiscaled flexible GaX NS/SWCNT heterostructures with abundant voids for Li + diffusion are fabricated by embedding the liquid-exfoliated GaX NS matrix within a SWCNT-percolated network; the latter improves the electron transport and ion diffusion kinetics as well as maintains the mechanical flexibility. Consequently, high capacities (i.e., 838 mAh g -1 per gallium (II) sulfide (GaS) NS/SWCNT mass and 1107 mAh g -1 per GaS mass; the latter is close to the theoretical value) and good rate capabilities are achieved, which can be majorly attributed to the alloying processes of disordered Ga formed after the first irreversible GaX conversion reaction, as monitored by in situ X-ray diffraction. The presented approach, colloidal solution processing of SWCNT and liquid-exfoliated MC NS to produce flexible paper-based electrode, could be generalized for wearable energy storage devices with promising performances. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Percolation based enhancement in effective thermal conductivity of ...

    Indian Academy of Sciences (India)

    empirical model, which is based on the argument that the enhanced thermal conductivity of high filler loaded compo- sites originates from forming conductive channels or, chains of fillers. Their expression contains two constants, C1 and. C2, which are experimentally determined and cannot be pre- cisely predicted. All these ...

  8. Colloidal gold-based immunochromatographic strip assay for the rapid detection of three natural estrogens in milk.

    Science.gov (United States)

    Wang, Zhongxing; Guo, Lingling; Liu, Liqiang; Kuang, Hua; Xu, Chuanlai

    2018-09-01

    In this study, we developed highly sensitive and specific monoclonal antibodies (mAbs) against estrone (E 1 ), 17β-estradiol (17β-E 2 ), and estriol (E 3 ). The half-maximal inhibitory concentration values of anti-E 1 , anti-17β-E 2 , and anti-E 3 mAbs were 0.46, 0.36, and 0.39 ng/mL, respectively, based on competitive enzyme-linked immunosorbent assay (ic-ELISA) results. A rapid colloidal gold-based immunoassay strip assay was developed for the determination of E 1, 17β-E 2 , and E 3 residues in milk samples. The assay had a visual cut-off value of 5 ng/mL, and required 10 min to assess with the naked eye. The results obtained from the immunochromatographic strip assay were consistent with those obtained from ic-ELISA and gas chromatography-mass spectrometry. The immunochromatographic strip assay is useful and rapid for the detection of E 1 , 17β-E 2 , and E 3 in milk. Copyright © 2018 Elsevier Ltd. All rights reserved.

  9. Detection of 3-phenoxybenzoic acid in river water with a colloidal gold-based lateral flow immunoassay.

    Science.gov (United States)

    Liu, Yuan; Wu, Aihua; Hu, Jing; Lin, Manman; Wen, Mengtang; Zhang, Xiao; Xu, Chongxin; Hu, Xiaodan; Zhong, Jianfeng; Jiao, Lingxia; Xie, Yajing; Zhang, Cunzhen; Yu, Xiangyang; Liang, Ying; Liu, Xianjin

    2015-08-15

    3-Phenoxybenzoic acid (3-PBA) is a general metabolite of synthetic pyrethroids. It could be used as a generic biomarker for multiple pyrethroids exposure for human or pyrethroid residues in the environment. In this study, monoclonal antibodies (mAbs) against 3-PBA were developed by using PBA-bovine serum albumin (BSA) as an immunogen. In the competitive enzyme-linked immunosorbent assay (ELISA) format, the I50 and I10 values of purified mAbs were 0.63 and 0.13 μg/ml, respectively, with a dynamic range between 0.19 and 2.04 μg/ml. Then, the colloidal gold (CG)-based lateral flow immunoassay was established based on the mAbs. The working concentration of coating antigen and CG-labeled antibodies and the blocking effects were investigated to get optimal assay performance. The cutoff value for the assay was 1 μg/ml 3-PBA, and the detection time was within 10 min. A total of 40 river water samples were spiked with 3-PBA at different levels and determined by the lateral flow immunoassay without any sample pretreatments. The negative false rate was 2.5%, and no positive false results were observed at these levels. This lateral flow immunoassay has the potential to be an on-site screening method for monitoring 3-PBA or pyrethroid residues in environmental samples. Copyright © 2015 Elsevier Inc. All rights reserved.

  10. Electrical conductivity, thermal conductivity, and rheological properties of graphene oxide-based nanofluids

    Science.gov (United States)

    Hadadian, Mahboobeh; Goharshadi, Elaheh K.; Youssefi, Abbas

    2014-12-01

    Highly stable graphene oxide (GO)-based nanofluids were simply prepared by dispersing graphite oxide with the average crystallite size of 20 nm, in polar base fluids without using any surfactant. Electrical conductivity, thermal conductivity, and rheological properties of the nanofluids were measured at different mass fractions and various temperatures. An enormous enhancement, 25,678 %, in electrical conductivity of distilled water was observed by loading 0.0006 mass fraction of GO at 25 °C. GO-ethylene glycol nanofluids exhibited a non-Newtonian shear-thinning behavior followed by a shear-independent region. This shear-thinning behavior became more pronounced at higher GO concentrations. The maximum ratio of the viscosity of nanofluid to that of the ethylene glycol as a base fluid was 3.4 for the mass fraction of 0.005 of GO at 20 °C under shear rate of 27.5 s-1. Thermal conductivity enhancement of 30 % was obtained for GO-ethylene glycol nanofluid for mass fraction of 0.07. The measurement of the transport properties of this new kind of nanofluid showed that it could provide an ideal fluid for heat transfer and electronic applications.

  11. Contactless Quality Monitoring Sensor Based on Electrical Conductivity Measurements

    Directory of Open Access Journals (Sweden)

    Armin SATZ

    2010-09-01

    Full Text Available A first prototype of a contactless conductivity sensor for AdBlue® quality monitoring is presented. Based on a detailed sensor mode analysis it is shown that capacitive sensors can be designed to sense electrical liquid conductivity. The sensor design process is based on a sensor model, which allows simulating capacitive senor responses for arbitrary electrode and liquid tank geometries. Finally, temperature induced errors are estimated.

  12. Colloid Transport and Retention

    DEFF Research Database (Denmark)

    Yuan, Hao; Shapiro, Alexander

    2012-01-01

    Book Description: Colloidal science and technology is one of the fastest growing research and technology areas. This book explores the cutting edge research in colloidal science and technology that will be usefull in almost every aspect of modern society. This book has a depth of information...... related to historical prospective, synthesis, characterization, theoretical modeling and application of unique class of colloidal materials starting from colloidal gold to coated silica colloid and platinum, titania colloids. This book is unique in its design, content, providing depth of science about...... different colloidal materials and their applications in chemistry, physics, biological, medical sciences and environment. Graduate students, academic and industrial researchers and medical professionals will discover recently developed colloidal materials and their applications in many areas of human...

  13. Colloid and surfactant

    International Nuclear Information System (INIS)

    Kuk, Yun Hwan; Lee, Jeong Jung; Cho, Sun Chae; Ryeo, Su Dong

    1995-08-01

    This book consists of two parts about colloid and surfactant. The first parts has explanations colloid and surface science, which deal with creation and properties of colloidal particles, surfactant and micelle colloid, property of surfactant, membranes, absorption of surface science, electrokinetic phenomenon, emulsion, foam and rheology. The second part mentions surfactant on anionic surfactant with five types, amphoteric surface active agent, non-ionic surface active agent and use of surfactant.

  14. Evaluation of Colloidal Stability and Ecotoxicity of Metal-based Nanoparticles in the Aquatic and Terrestrial Systems

    Science.gov (United States)

    Pokhrel, Lok Raj

    Intrinsic to the many nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. This Ph.D. dissertation is designed to investigate (i) whether metals or oxide nanoparticles are more toxic than ions, and if MetPLATE(TM) bioassay is applicable as a rapid nanotoxicity screening tool; (ii) how variable water chemistry (dissolved organic carbon (DOC), pH, and hardness) and organic compounds (cysteine, humic acid, and trolox) modulate colloidal stability, ion release, and aquatic toxicity of silver nanoparticles (AgNP); and (iii) the developmental responses of crop plants exposed to Ag- or ZnO- (zinc oxide) nanoparticles. Results suggest that the MetPLATE can be considered a high-throughput screening tool for rapid nanotoxicity evaluation. Detectable changes in the colloidal diameter, surface charge, and plasmonic resonance revealed modulating effects of variable water chemistry and organic ligands on the particle stability, dissolution, and toxicity of AgNPs against Escherichia coli or Daphnia magna. Silver dissolution increased as a function of DOC concentrations but decreased with increasing hardness, pH, cysteine, or trolox levels. Notably, the dissociated Ag+ was inadequate to explain AgNP toxicity, and that the combined effect of AgNPs and dissolved Ag+ under each ligand treatment was lower than of AgNO 3. Significant attenuation by trolox signifies an oxidative stress-mediated AgNP toxicity; its inability to attenuate AgNO3 toxicity, however, negates oxidative stress as Ag+ toxicity mechanism, and that cysteine could effectively quench free Ag+ to alleviate AgNO 3 toxicity in D. magna. Surprisingly, DOC-AgNPs complex that apparently formed at higher DOC levels might have led daphnids filter-feed on aggregates, potentially elevating internal dose, and thus higher mortality. Maize root anatomy showed differential alterations upon exposure to Ag

  15. Active structuring of colloidal armour on liquid drops

    OpenAIRE

    Dommersnes, Paul; Rozynek, Zbigniew; Mikkelsen, Alexander; Castberg, Rene; Kjerstad, Knut; Hersvik, Kjetil; Fossum, Jon Otto

    2013-01-01

    Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-fieldassisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a...

  16. Dual soft-template system based on colloidal chemistry for the synthesis of hollow mesoporous silica nanoparticles.

    Science.gov (United States)

    Li, Yunqi; Bastakoti, Bishnu Prasad; Imura, Masataka; Tang, Jing; Aldalbahi, Ali; Torad, Nagy L; Yamauchi, Yusuke

    2015-04-20

    A new dual soft-template system comprising the asymmetric triblock copolymer poly(styrene-b-2-vinyl pyridine-b-ethylene oxide) (PS-b-P2VP-b-PEO) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to synthesize hollow mesoporous silica (HMS) nanoparticles with a center void of around 17 nm. The stable PS-b-P2VP-b-PEO polymeric micelle serves as a template to form the hollow interior, while the CTAB surfactant serves as a template to form mesopores in the shells. The P2VP blocks on the polymeric micelles can interact with positively charged CTA(+) ions via negatively charged hydrolyzed silica species. Thus, dual soft-templates clearly have different roles for the preparation of the HMS nanoparticles. Interestingly, the thicknesses of the mesoporous shell are tunable by varying the amounts of TEOS and CTAB. This study provides new insight on the preparation of mesoporous materials based on colloidal chemistry. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Characterization of Metal Ion ­ Colloid Interaction: Impact On Colloid-facilitated Transport

    Science.gov (United States)

    Specht, C. H.; Schmitt, D.; Kaulisch, E.-M.; Frimmel, F. H.

    It is generally accepted, that metal transport in natural aquatic systems strongly de- pends on the metal binding form. Besides complex formation with well defined inor- ganic and organic ligands, the interaction with colloidal particles and soil material is one of the most important reactions of metal ions in aquatic systems. Mobile colloids compete with the stationary soil matrix for binding of metal ions and might facili- tate their transport. Important representatives for mineral and organic colloids are clay minerals and natural organic matter (NOM), respectively. In this work, the interaction of metal ions with clay minerals and NOM is characterized by coupling of asymmetric flow field-flow fractionation AF4 to inductively coupled plasma ­ mass spectrometry (ICPMS). A method for separating mineral from organic colloids is presented, which allows to quantify the amount of metals being bound to either colloid. For different metal ions (Cu, Zn, Pb, Pt) and a metalloid (As) a different extent of binding to either colloid was found.The information obtained from the AF4-ICPMS measurements was useful for the understanding of the observations from column experiments which were conducted to quantify the colloid-facilitated metal transport. In column experiments, the transport of the mineral colloids itself and the influence of NOM onto the colloid transport were investigated. Furthermore, the dependance of colloid transport from the ionic strength and the pH value was elucidated. In order to get information about the co-transport of metal ions by organic and mineral colloids, metal ions were adsorbed onto the colloidal material and a distribution coef- ficient of the metal ions between the colloidal phase and the solution was determined. The colloidal suspension containing both, "free" and adsorbed metal ions were then injected onto the column. The direct metal breakthrough caused by colloidal trans- port was detected at the column outlet. The results clearly

  18. Conductivity and transport studies of plasticized chitosan-based proton conducting biopolymer electrolytes

    International Nuclear Information System (INIS)

    Shukur, M F; Yusof, Y M; Zawawi, S M M; Illias, H A; Kadir, M F Z

    2013-01-01

    This paper focuses on the conductivity and transport properties of chitosan-based solid biopolymer electrolytes containing ammonium thiocyanate (NH 4 SCN). The sample containing 40 wt% NH 4 SCN exhibited the highest conductivity value of (1.81 ± 0.50) × 10 −4  S cm −1 at room temperature. Conductivity has increased to (1.51 ± 0.12) × 10 −3  S cm −1 with the addition of 25 wt% glycerol. The temperature dependence of conductivity for both salted and plasticized systems obeyed the Arrhenius rule. The activation energy (E a ) was calculated for both systems and it is found that the sample with 40 wt% NH 4 SCN in the salted system obtained an E a value of 0.148 eV and that for the sample containing 25 wt% glycerol in the plasticized system is 0.139 eV. From the Fourier transform infrared studies, carboxamide and amine bands shifted to lower wavenumbers, indicating that chitosan has interacted with NH 4 SCN salt. Changes in the C–O stretching vibration band intensity are observed at 1067 cm −1 with the addition of glycerol. The Rice and Roth model was used to explain the transport properties of the salted and plasticized systems. (paper)

  19. Conductivity and transport studies of plasticized chitosan-based proton conducting biopolymer electrolytes

    Science.gov (United States)

    Shukur, M. F.; Yusof, Y. M.; Zawawi, S. M. M.; Illias, H. A.; Kadir, M. F. Z.

    2013-11-01

    This paper focuses on the conductivity and transport properties of chitosan-based solid biopolymer electrolytes containing ammonium thiocyanate (NH4SCN). The sample containing 40 wt% NH4SCN exhibited the highest conductivity value of (1.81 ± 0.50) × 10-4 S cm-1 at room temperature. Conductivity has increased to (1.51 ± 0.12) × 10-3 S cm-1 with the addition of 25 wt% glycerol. The temperature dependence of conductivity for both salted and plasticized systems obeyed the Arrhenius rule. The activation energy (Ea) was calculated for both systems and it is found that the sample with 40 wt% NH4SCN in the salted system obtained an Ea value of 0.148 eV and that for the sample containing 25 wt% glycerol in the plasticized system is 0.139 eV. From the Fourier transform infrared studies, carboxamide and amine bands shifted to lower wavenumbers, indicating that chitosan has interacted with NH4SCN salt. Changes in the C-O stretching vibration band intensity are observed at 1067 cm-1 with the addition of glycerol. The Rice and Roth model was used to explain the transport properties of the salted and plasticized systems.

  20. Effect of desorption kinetics on colloid-facilitated transport of contaminants: Cesium, strontium, and illite colloids

    Science.gov (United States)

    Turner, Ned B.; Ryan, Joseph N.; Saiers, James E.

    2006-12-01

    To examine the importance of desorption kinetics to colloid-facilitated transport, we conducted column experiments comparing the transport of cesium and strontium through a saturated quartz sand porous medium in the absence and presence of illite colloids at two ionic strengths. Because cesium desorption from illite was anticipated to be slower than that of strontium, we expected to see a contrast in the colloid-facilitated transport of the cations. A model of colloid-facilitated transport accounting for second-order cation adsorption to and desorption from the quartz, second-order cation adsorption to and desorption from fast and slow sites on the illite colloids, and second-order colloid deposition to and release from the quartz accurately simulated the cation transport in the absence and presence of the illite colloids. The column results and model simulations revealed that cesium desorption was indeed slower than strontium desorption and that this contrast in desorption kinetics resulted in greater colloid-facilitated transport of the cesium. The desorption of both cations was slow relative to the rate of advection. The fast and slow sites on the illite colloids behaved like planar and frayed edge sites typically identified for cesium adsorption to illite. The amount of cesium adsorbed to the slow, or frayed edge, sites was similar to the frayed edge site density of illite estimated by other researchers.

  1. Electrical studies on silver based fast ion conducting glassy materials

    International Nuclear Information System (INIS)

    Rao, B. Appa; Kumar, E. Ramesh; Kumari, K. Rajani; Bhikshamaiah, G.

    2014-01-01

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag 2 O−[(1−x)B 2 O 3 −xTeO 2 ] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO 2 as well as with temperature. The conductivity of the present glass system is found to be of the order of 10 −2 S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries

  2. MR-based conductivity imaging using multiple receiver coils.

    Science.gov (United States)

    Lee, Joonsung; Shin, Jaewook; Kim, Dong-Hyun

    2016-08-01

    To propose a signal combination method for MR-based tissue conductivity mapping using a standard clinical scanner with multiple receiver coils. The theory of the proposed method is presented with two practical approaches, a coil-specific approach and a subject-specific approach. Conductivity maps were reconstructed using the transceive phase of the combined signal. The sensitivities of the coefficients used for signal combination were analyzed and the method was compared with other signal combination methods. For validation, multiple receiver brain coils and multiple receiver breast coils were used in phantom, in vivo brain, and in vivo breast studies. The variation among the conductivity estimates was conductivity estimates. MR-based tissue conductivity mapping is feasible when using a standard clinical MR scanner with multiple receiver coils. The proposed method reduces systematic errors in phase-based conductivity mapping that can occur due to the inhomogeneous magnitude of the combined receive profile. Magn Reson Med 76:530-539, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  3. Analyses of kinetic glass transition in short-range attractive colloids based on time-convolutionless mode-coupling theory.

    Science.gov (United States)

    Narumi, Takayuki; Tokuyama, Michio

    2017-03-01

    For short-range attractive colloids, the phase diagram of the kinetic glass transition is studied by time-convolutionless mode-coupling theory (TMCT). Using numerical calculations, TMCT is shown to recover all the remarkable features predicted by the mode-coupling theory for attractive colloids: the glass-liquid-glass reentrant, the glass-glass transition, and the higher-order singularities. It is also demonstrated through the comparisons with the results of molecular dynamics for the binary attractive colloids that TMCT improves the critical values of the volume fraction. In addition, a schematic model of three control parameters is investigated analytically. It is thus confirmed that TMCT can describe the glass-glass transition and higher-order singularities even in such a schematic model.

  4. Evaluation of point-of-care analyzers' ability to reduce bias in conductivity-based hematocrit measurement during cardiopulmonary bypass

    NARCIS (Netherlands)

    Teerenstra, S.; Steinfelder-Visscher, J.; Gunnewiek, J.K.; Weerwind, P.W.

    2014-01-01

    Most point-of-care testing analyzers use the conductivity method to measure hematocrit (hct). During open-heart surgery, blood-conductivity is influenced by shifts in electrolyte and colloid concentrations caused by infusion media used, and this may lead to considerable bias in the hct measurement.

  5. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. Viswanathan; P. Reimus

    2003-09-05

    Colloid retardation is influenced by the attachment and detachment of colloids from immobile surfaces. This analysis demonstrates the development of parameters necessary to estimate attachment and detachment of colloids and, hence, retardation in both fractured tuff and porous alluvium. Field and experimental data specific to fractured tuff are used for the analysis of colloid retardation in fractured tuff. Experimental data specific to colloid transport in alluvial material from Yucca Mountain as well as bacteriophage field studies in alluvial material, which are thought to be good analogs for colloid transport, are used to estimate attachment and detachment of colloids in the alluvial material. There are no alternative scientific approaches or technical methods for calculating these retardation factors.

  6. Colloid characterization and in situ release in shallow groundwater under different hydrogeology conditions.

    Science.gov (United States)

    Zhou, Jingjing; Liu, Dan; Zhang, Wenjing; Chen, Xuequn; Huan, Ying; Yu, Xipeng

    2017-06-01

    Changes to groundwater hydrodynamics and chemistry can lead to colloid release that can have a major impact on the groundwater environment. To analyze the effects of colloid release caused by artificial groundwater recharge, field and laboratory tests on colloid characterization and colloid release were conducted. The field tests were carried out at an artificial recharge test site in Shandong Province. In the field investigation, one recharge water sample and five groundwater samples were collected and filtered through three levels of ultrafiltration membranes, with pore sizes of 0.45 μm, 100 kDa, and 50 kDa. The field results indicated that the colloid mass concentrations in groundwater retained between membranes with pore sizes of 100 kDa-0.45 μm and 50 kDa-100 kDa were 19 and 62 mg/L, respectively. In recharge water, the colloid mass concentrations retained by 100-kDa-0.45-μm and 50-kDa-100-kDa membranes were 3 and 99 mg/L, respectively. Colloids detected on the ultrafiltration membranes were mainly inorganic between 100 kDa and 0.45 μm, and mainly organic between 50 and 100 kDa. Based on the field colloid investigation results, the organic colloid was chosen in the laboratory experiments to reveal its release behavior under different conditions. Porous media diameter, flux, ionic strength (IS), and ion valence were changed to determine their influences on organic colloid concentration outflow from undisturbed porous media. The experiment's results indicate that decreasing the diameter, and increasing the flux, ionic strength, and the number of divalent cations, can promote organic colloid release. The organic colloid release rate in the early stage was high and is thus likely to affect the quality of groundwater. The results provide a useful scientific basis for minimizing changes to hydrodynamic and hydrochemical conditions during artificial recharge, thus safeguarding groundwater quality.

  7. Thermally Conductive Tape Based on Carbon Nanotube Arrays

    Science.gov (United States)

    Kashani, Ali

    2011-01-01

    array of CNTs was measured to be as high as 10 W/K. The high thermal conductivity and the nanoscale size make CNTs ideal as thermal interface materials. The CNT-based thermal tape can be used for the thermal management of microelectronic packages and electronic systems. It also can be integrated with current device technology and packaging. The material would allow for an efficient method to manage excess heat generation without requiring any additional power. Lastly, the CNT tape can be used to enhance thermal contact conductance across two mating surfaces on some NASA missions.

  8. Enhanced electrical conductivity in Xe ion irradiated CNT based transparent conducting electrode on PET substrate

    Science.gov (United States)

    Surbhi; Sharma, Vikas; Singh, Satyavir; Garg, Priyanka; Asokan, K.; Sachdev, Kanupriya

    2018-02-01

    An investigation of MWCNT-based hybrid electrode films with improved electrical conductivity after Xe ion irradiation is reported. A multilayer hybrid structure of Ag-MWCNT layer embedded in between two ZnO layers was fabricated and evaluated, pre and post 100 keV Xe ion irradiation, for their performance as Transparent Conducting Electrode in terms of their optical and electrical properties. X-ray diffraction pattern exhibits highly c-axis oriented ZnO films with a small variation in lattice parameters with an increase in ion fluence. There is no significant change in the surface roughness of these films. Raman spectra were used to confirm the presence of CNT. The pristine multilayer films exhibit an average transmittance of ˜70% in the entire visible region and the transmittance increases with Xe ion fluence. A significant enhancement in electrical conductivity post-Xe ion irradiation viz from 1.14 × 10-7 Ω-1 cm-1 (pristine) to 7.04 × 103 Ω-1 cm-1 is seen which is due to the high connectivity in the top layer with Ag-CNT hybrid layer facilitating the smooth transfer of electrons.

  9. Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds

    OpenAIRE

    Dharmshaktu, Ganesh Singh; Singhal, Aanshu; Pangtey, Tanuja

    2016-01-01

    A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of ...

  10. Polydopamine-Based 3D Colloidal Photonic Materials: Structural Color Balls and Fibers from Melanin-Like Particles with Polydopamine Shell Layers.

    Science.gov (United States)

    Kohri, Michinari; Yanagimoto, Kenshi; Kawamura, Ayaka; Hamada, Kosuke; Imai, Yoshihiko; Watanabe, Takaichi; Ono, Tsutomu; Taniguchi, Tatsuo; Kishikawa, Keiki

    2018-03-07

    Nature creates beautiful structural colors, and some of these colors are produced by nanostructural arrays of melanin. Polydopamine (PDA), an artificial black polymer produced by self-oxidative polymerization of dopamine, has attracted extensive attention because of its unique properties. PDA is a melanin-like material, and recent studies have reported that photonic materials based on PDA particles showed structural colors by enhancing color saturation through the absorption of scattered light. Herein, we describe the preparation of three-dimensional (3D) colloidal photonic materials, such as structural color balls and fibers, from biomimetic core-shell particles with melanin-like PDA shell layers. Structural color balls were prepared through the combined use of membrane emulsion and heating. We also demonstrated the use of microfluidic emulsification and solvent diffusion for the fabrication of structural color fibers. The obtained 3D colloidal materials, i.e., balls and fibers, exhibited angle-independent structural colors due to the amorphous assembly of PDA-containing particles. These findings provide new insight for the development of dye-free technology for the coloration of various 3D colloidal architectures.

  11. [Mentalization Based Treatment of an Adolescent Girl with Conduct Disorder].

    Science.gov (United States)

    Reiter, Melanie; Bock, Astrid; Althoff, Marie-Luise; Taubner, Svenja; Sevecke, Kathrin

    2017-05-01

    Mentalization Based Treatment of an Adolescent Girl with Conduct Disorder This paper will give a short overview on the theoretical concept of mentalization and its specific characteristics in adolescence. A previous study on Mentalization based treatment for adolescents (MBT-A) demonstrated the effectiveness of MBT-A for the treatment of adolescents with symptoms of deliberate self-harm (Rossouw u. Fonagy, 2012). Based on the results of this study Taubner, Gablonski, Sevecke, and Volkert (in preparation) developed a manual for mentalization based treatment for adolescents with conduct disorders (MBT-CD). This manual represents the foundation for a future study on the efficacy of the MBT-A for this specific disorder in young people. The present case report demonstrates the application of specific MBT interventions, as well as the therapeutic course over one year in a 16-year old girl who fulfilled all criteria of a conduct disorder. During the course of treatment, the de-escalating relationship-oriented therapeutic approach can be considered as a great strength of MBT-A, especially for patients with conduct disorders. The clinical picture, as well as the psychological assessment, showed a positive progress over the course of treatment. Despite frequent escalations, forced placements due to acute endangerment of self and others, and a precarious situation with the patient's place of residence towards the end of therapy, MBT-A treatment enabled the patient to continually use the evolved mentalizing capabilities as a resource.

  12. Ionic conductivity and diffusion coefficient of barium-chloride-based ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 4. Ionic conductivity and diffusion coefficient of barium-chloride-based polymer electrolyte with poly(vinyl alcohol)–poly(4-styrenesulphonic acid) polymer complex. MAYANK PANDEY GIRISH M JOSHI NARENDRA NATH GHOSH. Volume 40 Issue 4 August ...

  13. Lithium ion conducting solid polymer blend electrolyte based on bio ...

    Indian Academy of Sciences (India)

    Lithium ion conducting polymer blend electrolyte films based on poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) with different Mwt% of lithium nitrate (LiNO3) salt, using a solution cast technique, have been prepared. The polymer blend electrolyte has been characterized by XRD, FTIR, DSC and impedance ...

  14. Graphene as anode electrode for colloidal quantum dots based light emitting diodes

    Science.gov (United States)

    Klekachev, Alexander V.; Kuznetsov, Sergey N.; Asselberghs, Inge; Cantoro, Mirco; Hun Mun, Jeong; Jin Cho, Byung; Stesmans, André L.; Heyns, Marc M.; De Gendt, Stefan

    2013-07-01

    Graphene films demonstrating low sheet resistance and high transparency in the visible light range are promising to be used as electrodes for light-emitting applications. In this work, we report the implementation of single layer graphene as hole injecting electrode for CdSe/ZnS quantum dot-light emitting diodes (QD-LED). We compare graphene vs. indium-tin-oxide (ITO)-based anode junctions by electroluminescence intensity performance of QD-LEDs. Our results demonstrate better hole injection efficiency for the graphene-based electrode at technologically relevant current densities J graphene as a valuable alternative to replace ITO in QD-LED technology.

  15. Colloidal silver-based nanogel as nonocclusive dressing for multiple superficial pellet wounds

    Directory of Open Access Journals (Sweden)

    Ganesh Singh Dharmshaktu

    2016-01-01

    Full Text Available A good dressing is mandatory to an uncomplicated wound healing, especially when foreign particles contaminate the wound. Various forms of dressing preparations are available for use and differ in chemical composition and efficacy. Silver has been a known agent with good antimicrobial and healing properties and recent times has seen an upsurge in various silver-based dressing supplements. We describe our report of use and efficacy of a silver nanoparticle- based gel dressing in the healing of multiple superficial firearm pellet wounds.

  16. Lateral-flow colloidal gold-based immunoassay for the rapid detection of deoxynivalenol with two indicator ranges

    Energy Technology Data Exchange (ETDEWEB)

    Kolosova, Anna Yu. [Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium)], E-mail: anna_kolosova@hotmail.com; Sibanda, Liberty [TOXI-TEST NV, Industrielaan 9a, 9990 Maldegem (Belgium); Dumoulin, Frederic [Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium); Lewis, Janet; Duveiller, Etienne [International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, 06600 Mexico, D.F. (Mexico); Van Peteghem, Carlos; Saeger, Sarah de [Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent (Belgium)

    2008-06-02

    A lateral-flow immunoassay using a colloidal gold-labelled monoclonal antibody was developed for the rapid detection of deoxynivalenol (DON). Different parameters, such as the amount of immunoreagents, type of the materials, composition of the blocking solution and of the detector reagent mixture, were investigated to provide the optimum assay performance. The experimental results demonstrated that such a visual test had an indicator range rather than a cut-off value. Thus, tests for DON determination with two different indicator ranges of 250-500 and 1000-2000 {mu}g kg{sup -1} were designed. The method allowed detection of DON at low and high concentration levels, which could be useful for research and practical purposes. The assay applied to spiked wheat and pig feed samples demonstrated accurate and reproducible results. The applicability of the developed lateral-flow test was also confirmed under real field conditions. The test strips prepared in Belgium were sent to Mexico, where they were used for the screening of DON contamination in different bread wheat entries from Fusarium Head Blight inoculated plots. The results were compared with those obtained by ELISA and LC-MS/MS. A poor correlation between ELISA and LC-MS/MS was observed. Visual results of the dipstick tests were in a good agreement with the results of the LC-MS/MS method. Coupled with a simple and fast sample preparation, this qualitative one-step test based on the visual evaluation of results did not require any equipment. Results could be obtained within 10 min. The described assay format can be used as a simple, rapid, cost-effective and robust on-site screening tool for mycotoxin contamination in different agricultural commodities.

  17. Transformative Colloidal Nanomaterials for Mid- Infrared Devices

    Science.gov (United States)

    2015-06-11

    conductivity in monodispersed colloidal nanocrystal films was observed first nearly a decade ago, 7 field-effect transistors achieve ever increasing...mobilities,8 there are reports of high sensitivity photoconduction,9 and photovoltaic performance is improving with already ~100% quantum efficiency.2 The...446 (2005) [2] Hillhouse, H.W., Beard, M.C., “Solar cells from colloidal nanocrystals: Fundamentals, materials, devices, and economics,” Curr. Op

  18. Lattice-Boltzmann-based simulations of diffusiophoresis of colloids and cells

    Science.gov (United States)

    Kreft Pearce, Jennifer; Castigliego, Joshua

    Increasing environmental degradation due to plastic pollutants requires innovative solutions that facilitate the extraction of pollutants without harming local biota. We present results from a lattice-Boltzmann-base Brownian Dynamics simulation on diffusiophoresis and the separation of particles within the system. A gradient in viscosity that simulates a concentration gradient in a dissolved polymer allows us to separate various types of particles based on their deformability. As seen in previous experiments, simulated particles that have a higher deformability react differently to the polymer matrix than those with a lower deformability. Therefore, the particles can be separated from each other. The system described above was simulated with various concentration gradients as well as various Soret coefficients in order to optimize the separation of the particles. This simulation, in particular, was intended to model an oceanic system where the particles of interest were motile and nonmotile plankton and microplastics. The separation of plankton from the microplastics was achieved.

  19. Proton Conductivity and Operational Features Of PBI-Based Membranes

    DEFF Research Database (Denmark)

    Qingfeng, Li; Jensen, Jens Oluf; Precht Noyé, Pernille

    2005-01-01

    As an approach to high temperature operation of PEMFCs, acid-doped PBI membranes are under active development. The membrane exhibits high proton conductivity under low water contents at temperatures up to 200°C. Mechanisms of proton conduction for the membranes have been proposed. Based on the me...... on the membranes fuel cell tests have been demonstrated. Operating features of the PBI cell include no humidification, high CO tolerance, better heat utilization and possible integration with fuel processing units. Issues for further development are also discussed....

  20. Colloid suspension stability and transport through unsaturated porous media

    Energy Technology Data Exchange (ETDEWEB)

    McGraw, M.A.; Kaplan, D.I.

    1997-04-01

    Contaminant transport is traditionally modeled in a two-phase system: a mobile aqueous phase and an immobile solid phase. Over the last 15 years, there has been an increasing awareness of a third, mobile solid phase. This mobile solid phase, or mobile colloids, are organic or inorganic submicron-sized particles that move with groundwater flow. When colloids are present, the net effect on radionuclide transport is that radionuclides can move faster through the system. It is not known whether mobile colloids exist in the subsurface environment of the Hanford Site. Furthermore, it is not known if mobile colloids would likely exist in a plume emanating from a Low Level Waste (LLW) disposal site. No attempt was made in this study to ascertain whether colloids would form. Instead, experiments and calculations were conducted to evaluate the likelihood that colloids, if formed, would remain in suspension and move through saturated and unsaturated sediments. The objectives of this study were to evaluate three aspects of colloid-facilitated transport of radionuclides as they specifically relate to the LLW Performance Assessment. These objectives were: (1) determine if the chemical conditions likely to exist in the near and far field of the proposed disposal site are prone to induce flocculation (settling of colloids from suspension) or dispersion of naturally occurring Hanford colloids, (2) identify the important mechanisms likely involved in the removal of colloids from a Hanford sediment, and (3) determine if colloids can move through unsaturated porous media.

  1. Pore water colloid properties in argillaceous sedimentary rocks.

    Science.gov (United States)

    Degueldre, Claude; Cloet, Veerle

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  2. Gum ghatti based novel electrically conductive biomaterials: A study of conductivity and surface morphology

    Directory of Open Access Journals (Sweden)

    S. Kalia

    2014-04-01

    Full Text Available Gum ghatti-cl-poly(acrylamide-aniline interpenetrating network (IPN was synthesized by a two-step aqueous polymerization method, in which aniline monomer was absorbed into the network of gum ghatti-cl-poly(acrylamide and followed by a polymerization reaction between aniline monomers. Initially, semi-IPN based on acrylamide and gum ghatti was prepared by free-radical copolymerization in aqueous media with optimized process parameters, using N,N'-methylenebis-acrylamide, as cross-linker and ammonium persulfate, as an initiator system. Optimum reaction conditions affording maximum percentage swelling were: solvent [mL] =12, Acrylamide (AAm [mol•L–1] = 1.971, Ammonium peroxydisulfate (APS [mol•L–1] = 0.131•10–1, N,N'-methylene-bis-acrylamide (MBA [mol•L–1] = 0.162•10–1, reaction time [min] = 210, temperature [°C] = 100 and pH = 7.0. The resulting IPN was doped with different protonic acids. The effect of the doping has been investigated on the conductivity and surface morphology of the IPN hydrogel. The maximum conductivity was observed with 1.5N HClO4 concentration. The morphological, structural and electrical properties of the candidate polymers were studied using scanning electron micrscopy (SEM, Fourier transform infrared spectroscopy FTIR and two-probe method, respectively.

  3. Evaluating the Mechanical Properties of Tomato Based on Electrical Conductivity

    Directory of Open Access Journals (Sweden)

    M Ghasemi

    2014-09-01

    Full Text Available Evaluation of mechanical and electrical properties of agricultural products plays an important role in equipment design and optimizing post-harvest operations. Among the crops, tomato and its products are the major processing industries in the world and its economic importance is increasing. Considering the importance of the quality and various post harvesting uses of tomato, the evaluation of mechanical properties including rupture force and deformation and the work done to establish the rupture of two tomato cultivars (Petoearly CH and Newton were studied under penetration test based on the electrical conductivity. These properties were measured at three levels of 1, 3 and 5 days after harvesting. The evaluated mechanical properties of both cultivars were decreased by increasing the storage time. Interaction of cultivar and time were significant at the 1% level, for all mechanical parameters except the deformation failure in both cultivars. The electrical conductivity of both cultivars was decreased by increasing the storage time. Interaction of cultivar and time on the electrical conductivity of both cultivars were significant at the 1% level. Significant relationships were found at the 1% level between electrical conductivity and mechanical properties except for deformation of Petoearly CH cultivar. Among the mechanical parameters, rupture forces and rupture works of both cultivars were highly correlated with the electrical conductivity.

  4. Unilateral NMR investigation of multifunctional treatments on stones based on colloidal inorganic and organic nanoparticles.

    Science.gov (United States)

    Di Tullio, Valeria; Cocca, Mariacristina; Avolio, Roberto; Gentile, Gennaro; Proietti, Noemi; Ragni, Pietro; Errico, Maria Emanuela; Capitani, Donatella; Avella, Maurizio

    2015-01-01

    Consolidation and protection are among the most important treatments usually carried out in conservation of stone artifacts and monuments. In this paper, portable unilateral NMR and conventional techniques were used for investigating new multifunctional treatments based on tetraethoxysilane, silica, and polytetrafluoroethylene nanoparticles. The study was carried out on a very complex and heterogeneous porous stone such as tuff. NMR study allowed to obtain detailed information on the penetration depth of treatments, the hydrophobic effect, and changes in the open porosity caused by treatments. Physical and chemical inhomogeneities between the impregnated layers of tuff and the layers underneath were also detected. The average pores radius and pores interconnection obtained from NMR diffusion measurements were used for the first time to compare effects of different consolidating and/or protective treatments on stone. Because unilateral NMR technique is neither destructive nor invasive, investigation of treatments can be also carried out and optimized directly on buildings and monuments of interest for Cultural Heritage. Copyright © 2014 John Wiley & Sons, Ltd.

  5. Analysis of colloid transport

    International Nuclear Information System (INIS)

    Travis, B.J.; Nuttall, H.E.

    1985-01-01

    The population balance methodology is described and applied to the transport and capture of polydispersed colloids in packed columns. The transient model includes particle growth, capture, convective transport, and dispersion. We also follow the dynamic accumulation of captured colloids on the solids. The multidimensional parabolic partial differential equation was solved by a recently enhanced method of characteristics technique. This computational technique minimized numerical dispersion and is computationally very fast. The FORTRAN 77 code ran on a VAX-780 in less than a minute and also runs on an IBM-AT using the Professional FORTRAN compiler. The code was extensively tested against various simplified cases and against analytical models. The packed column experiments by Saltelli et al. were re-analyzed incorporating the experimentally reported size distribution of the colloid feed material. Colloid capture was modeled using a linear size dependent filtration function. The effects of a colloid size dependent filtration factor and various initial colloid size distributions on colloid migration and capture were investigated. Also, we followed the changing colloid size distribution as a function of position in the column. Some simple arguments are made to assess the likelihood of colloid migration at a potential NTS Yucca Mountain waste disposal site. 10 refs., 3 figs., 1 tab

  6. UZ Colloid Transport Model

    International Nuclear Information System (INIS)

    McGraw, M.

    2000-01-01

    The UZ Colloid Transport model development plan states that the objective of this Analysis/Model Report (AMR) is to document the development of a model for simulating unsaturated colloid transport. This objective includes the following: (1) use of a process level model to evaluate the potential mechanisms for colloid transport at Yucca Mountain; (2) Provide ranges of parameters for significant colloid transport processes to Performance Assessment (PA) for the unsaturated zone (UZ); (3) Provide a basis for development of an abstracted model for use in PA calculations

  7. Colloid process engineering

    CERN Document Server

    Peukert, Wolfgang; Rehage, Heinz; Schuchmann, Heike

    2015-01-01

    This book deals with colloidal systems in technical processes and the influence of colloidal systems by technical processes. It explores how new measurement capabilities can offer the potential for a dynamic development of scientific and engineering, and examines the origin of colloidal systems and its use for new products. The future challenges to colloidal process engineering are the development of appropriate equipment and processes for the production and obtainment of multi-phase structures and energetic interactions in market-relevant quantities. The book explores the relevant processes and for controlled production and how they can be used across all scales.

  8. Anhydrous proton conductivity of acid doped vinyltriazole-based polymers

    International Nuclear Information System (INIS)

    Pu, Hongting; Ye, Sheng; Wan, Decheng

    2007-01-01

    Poly(1,2,4-vinyltriazole) (PVTr) and poly(1,2,4-vinyltriazole-co-5-vinyltetrazole-co-acrylonitrile) (P(VTr-VT-AN)) were prepared by normal free radical polymerization and click chemistry, respectively. The structure of the polymers was characterized by FTIR spectra, H NMR spectrum and elemental analysis. Compared with polybenzimidazole (PBI) which is one of the most widely studied anhydrous proton conducting polymers, the solubility of vinyltriazole-based polymers is improved significantly. They are soluble in a lot of polar solvents. The glass-transition temperatures of such kind of polymers are between 70 and 85 o C, thus indirectly indicating the improvement of fabricating properties. In phosphoric acid doped membranes, the higher the basicity of the vinyltriazole-based polymers is, the higher the proton conductivity is. The temperature dependence of the proton conductivity of the acid doped membranes can always be fitted by a simple Arrhenius equation. Transmittance of phosphoric acid doped vinyltriazole-based polymers is above 80% in the range of visual spectra and changes a little with the different structure and basicity of the copolymers

  9. Pore water colloid properties in argillaceous sedimentary rocks

    Energy Technology Data Exchange (ETDEWEB)

    Degueldre, Claude, E-mail: c.degueldre@lancaster.ac.uk [Engineering Department, University of Lancaster, LA1 4YW Lancaster (United Kingdom); ChiAM & Institute of Environment, University of Geneva, 1211 Genève 4, Swizerland (Switzerland); Earlier, NES, Paul Scherrer Institute, 5232 Villigen (Switzerland); Cloet, Veerle [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  10. Preferences for colloid use in Scandinavian intensive care units.

    Science.gov (United States)

    2008-07-01

    Fluid resuscitation is a frequent intervention in intensive care. Colloids are widely used, but recent data suggest harm by some of these solutions. This calls for more clinical studies on this matter, but the current preferences for colloid use in Scandinavian intensive care units (ICUs) are unknown. In March-May 2007, 120 Scandinavian ICUs were invited to answer a web-based survey consisting of 18 questions on types of colloids, indications, contraindications and rationale of use. Seventy-three ICUs, of which 31 were university hospital units, answered the questionnaire. Most ICUs used both synthetic and natural colloids, and hydroxyethyl starch (HES) 130/0.4 was the preferred colloid in 59 units. Eleven ICUs had protocols for colloid use. The most frequent indication was second-line fluid for hypovolaemia, but one in three ICUs used colloids as first-line fluid. Thirty-five ICUs had contraindications, which were mainly for the use of synthetic colloids (acute renal failure 25 units, bleeding 15 units). Most units based the use of colloids on theoretical knowledge and tradition. Sixty-five and 54 ICUs were ready to change colloid use based on data from randomised trials of ICU patients showing changes in mortality or renal function, respectively. Most Scandinavian ICUs use both synthetic and natural colloids, but HES 130/0.4 is by far the preferred colloid. Few units have protocols for colloid use, but most use them for hypovolaemia, and the majority have no contraindications. Most ICUs are ready to change colloid use if randomised trials in ICU patients show changes in mortality or renal function.

  11. Microbial effects on colloidal agglomeration

    International Nuclear Information System (INIS)

    Hersman, L.

    1995-11-01

    Colloidal particles are known to enhance the transport of radioactive metals through soil and rock systems. This study was performed to determine if a soil microorganism, isolated from the surface samples collected at Yucca Mountain, NV, could affect the colloidal properties of day particles. The agglomeration of a Wyoming bentonite clay in a sterile uninoculated microbial growth medium was compared to the agglomeration in the medium inoculated with a Pseudomonas sp. In a second experiment, microorganisms were cultured in the succinate medium for 50 h and removed by centrifugation. The agglomeration of the clay in this spent was compared to sterile uninoculated medium. In both experiments, the agglomeration of the clay was greater than that of the sterile, uninoculated control. Based on these results, which indicate that this microorganism enhanced the agglomeration of the bentonite clay, it is possible to say that in the presence of microorganisms colloidal movement through a rock matrix could be reduced because of an overall increase in the size of colloidal particle agglomerates. 32 refs

  12. Characterization of Complex Colloidal Suspensions

    Science.gov (United States)

    Seaman, J. C.; Guerin, M.; Jackson, B. P.; Ranville, J. M.

    2003-04-01

    Surface chemical reactions play a major role in controlling contaminant fate and transport in the subsurface environment. Recent field and laboratory evidence suggests that mobile soil and groundwater colloids may facilitate the migration of sparingly soluble groundwater contaminants. Colloidal suspensions collected in the field or generated in laboratory column experiments tend to be fairly dilute in nature and comprised of relatively small particulates (reserved for studying ideal systems to the characterization of mobile colloids. However, many of these analytical techniques, including total/selective dissolution methods, dynamic light scattering, micro-electrophoresis, streaming potential, and even scanning electron microscopy (SEM), can be biased in of larger size fractions, and therefore, extremely sensitive to sampling, storage, and fractionation artifacts. In addition, surface modifiers such as sorbed oxides or organics can alter particulate appearance, composition, and behavior when compared to synthetic analogues or mineral standards. The current presentation will discuss the limitations and inherent biases associated with a number of analytical characterization techniques that are commonly applied to the study of mobile soil and groundwater colloids, including field flow fractionation (FFF) and acoustic based methods that have only recently become available.

  13. Active structuring of colloidal armour on liquid drops

    Science.gov (United States)

    Dommersnes, Paul; Rozynek, Zbigniew; Mikkelsen, Alexander; Castberg, Rene; Kjerstad, Knut; Hersvik, Kjetil; Otto Fossum, Jon

    2013-06-01

    Adsorption and assembly of colloidal particles at the surface of liquid droplets are at the base of particle-stabilized emulsions and templating. Here we report that electrohydrodynamic and electro-rheological effects in leaky-dielectric liquid drops can be used to structure and dynamically control colloidal particle assemblies at drop surfaces, including electric-field-assisted convective assembly of jammed colloidal ‘ribbons’, electro-rheological colloidal chains confined to a two-dimensional surface and spinning colloidal domains on that surface. In addition, we demonstrate the size control of ‘pupil’-like openings in colloidal shells. We anticipate that electric field manipulation of colloids in leaky dielectrics can lead to new routes of colloidosome assembly and design for ‘smart armoured’ droplets.

  14. Fabrication of size-controllable hexagonal non-close-packed colloidal crystals and binary colloidal crystals by pyrolysis combined with plasma-electron co-irradiation of polystyrene colloidal monolaye

    International Nuclear Information System (INIS)

    Kim, Jae Joon

    2011-02-01

    We present an unprecedented and systematic route to controllably fabricate hexagonal non-close-packed (HNCP) monolayer colloidal crystals and binary colloidal crystals (BCCs) based on plasma-electron co-irradiation of polystyrene colloidal monolayers followed by thermal decomposition. HNCP colloidal crystals with tunable particle sizes and periods could be fabricated by changing the pristine colloidal particle size and the thermal decomposition time. In addition, BCCs and trimodal colloidal crystals that are composed of different-sized colloidal particles can also be fabricated by adding small particles on the prepared HNCP colloidal crystals. Both the particle size ratio and the volume fraction of the BCCs can be widely tuned. These HNCP colloidal crystals and BCCs have various potential applications as optical and photonic materials as well as in catalysis and sensors

  15. A novel PTFE-based proton-conductive membrane

    Science.gov (United States)

    Reichman, S.; Duvdevani, T.; Aharon, A.; Philosoph, M.; Golodnitsky, D.; Peled, E.

    The demand for a solid polymer electrolyte membrane (SPEM) for fuel-cell systems, capable of withstanding temperatures above 130 °C, decreasing the electrode-catalyst loadings and reducing poisoning by carbon monoxide, has prompted this study. A novel, low-cost, highly conductive, nanoporous proton-conducting membrane (NP-PCM) based on a polytetrafluoroethylene (PTFE) backbone has been developed. It comprises non-conductive nano-size ceramic powder, PTFE binder and an aqueous acid. The preparation procedures were studied and the membrane was characterized with the use of: SEM, EDS, pore-size-distribution measurements (PSD), TGA-DTA and electrochemical methods. The ionic conductivity of a membrane doped with 3 M sulfuric acid increases with the ceramic powder content and reaches 0.22 S cm -1 at 50% (v/v) silica. A non-optimized direct-methanol fuel cell (DMFC) with a 250 μm thick membrane has been assembled. It demonstrated 50 and 130 mW cm -2 at 80 and 130 °C, respectively. Future study will be directed to improving the membrane-preparation process, getting thinner membranes and using this membrane in a hydrogen-fed fuel cell.

  16. Fabrication of Biosensors Based on Nanostructured Conducting Polyaniline (NSPANI

    Directory of Open Access Journals (Sweden)

    Deepshikha SAINI

    2011-11-01

    Full Text Available In this study, glucose and hydrogen peroxide (H2O2 biosensors based on nanostructured conducting polyaniline (NSPANI (synthesized using sodiumdodecyl sulphate (SDS as structure directing agent were developed. Because of the large specific surface area, excellent conductivity of NSPANI, horseradish peroxidase (HRP and glucose oxidase (GOx could be easily immobilized with high loading and activity. In addition the small dimensions and the high surface-to-volume ratio of the NSCP allow the rapid transmission of electron and enhance current response. The linear dynamic range of optical glucose and H2O2 biosensors is 5–40 mM for glucose and 1–50 mM for H2O2, respectively where as the bulk PANI exhibits linearity between 5-20 mM/l. The miniature optical glucose biosensor also exhibits good reproducibility. The storage stability of optical glucose and H2O2 biosensors is two weeks for glucose and five days for H2O2. The high response value of NSPANI based biosensors as compared to bulk PANI based biosensor reflects higher enzymatic affinity of GOx/NSPANI and HRP/NSPANI with glucose and H2O2 due to biocompatibility, active surface area and high electron communication capability of nanobiopolymer film. In conclusion, the NSPANI based biosensors proposed herein have many advantages such as a low response time, high reproducibility, high sensitivity, stable and wide dynamic range.

  17. Thermal Conductivity Based on Modified Laser Flash Measurement

    Science.gov (United States)

    Lin, Bochuan; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2005-01-01

    The laser flash method is a standard method for thermal diffusivity measurement. It employs single-pulse heating of one side of a thin specimen and measures the temperature response of the other side. The thermal diffusivity of the specimen can be obtained based on a one-dimensional transient heat transfer analysis. This paper reports the development of a theory that includes a transparent reference layer with known thermal property attached to the back of sample. With the inclusion of heat conduction from the sample to the reference layer in the theoretical analysis, the thermal conductivity and thermal diffusivity of sample can be extracted from the temperature response data. Furthermore, a procedure is established to select two points from the data to calculate these properties. The uncertainty analysis indicates that this method can be used with acceptable levels of uncertainty.

  18. Interface colloidal robotic manipulator

    Science.gov (United States)

    Aronson, Igor; Snezhko, Oleksiy

    2015-08-04

    A magnetic colloidal system confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters. The colloidal system exhibits locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, structures can capture, transport, and position target particles.

  19. Purification technologies for colloidal nanocrystals.

    Science.gov (United States)

    Shen, Yi; Gee, Megan Y; Greytak, A B

    2017-01-10

    Almost all applications of colloidal nanocrystals require some type of purification or surface modification process following nanocrystal growth. Nanocrystal purification - the separation of nanocrystals from undesired solution components - can perturb the surface chemistry and thereby the physical properties of colloidal nanocrystals due to changes in solvent, solute concentrations, and exposure of the nanocrystal surface to oxidation or hydrolysis. For example, nanocrystal quantum dots frequently exhibit decreased photoluminescence brightness after precipitation from the growth solvent and subsequent redissolution. Consequently, purification is an integral part of the synthetic chemistry of colloidal nanocrystals, and the effect of purification methods must be considered in order to accurately compare and predict the behavior of otherwise similar nanocrystal samples. In this Feature Article we examine established and emerging approaches to the purification of colloidal nanoparticles from a nanocrystal surface chemistry viewpoint. Purification is generally achieved by exploiting differences in properties between the impurities and the nanoparticles. Three distinct properties are typically manipulated: polarity (relative solubility), electrophoretic mobility, and size. We discuss precipitation, extraction, electrophoretic methods, and size-based methods including ultracentrifugation, ultrafiltration, diafiltration, and size-exclusion chromatography. The susceptibility of quantum dots to changes in surface chemistry, with changes in photoluminescence decay associated with surface chemical changes, extends even into the case of core/shell structures. Accordingly, the goal of a more complete description of quantum dot surface chemistry has been a driver of innovation in colloidal nanocrystal purification methods. We specifically examine the effect of purification on surface chemistry and photoluminescence in quantum dots as an example of the challenges associated with

  20. Microrheology of colloidal systems

    International Nuclear Information System (INIS)

    Puertas, A M; Voigtmann, T

    2014-01-01

    Microrheology was proposed almost twenty years ago as a technique to obtain rheological properties in soft matter from the microscopic motion of colloidal tracers used as probes, either freely diffusing in the host medium, or subjected to external forces. The former case is known as passive microrheology, and is based on generalizations of the Stokes–Einstein relation between the friction experienced by the probe and the host-fluid viscosity. The latter is termed active microrheology, and extends the measurement of the friction coefficient to the nonlinear-response regime of strongly driven probes. In this review article, we discuss theoretical models available in the literature for both passive and active microrheology, focusing on the case of single-probe motion in model colloidal host media. A brief overview of the theory of passive microrheology is given, starting from the work of Mason and Weitz. Further developments include refined models of the host suspension beyond that of a Newtonian-fluid continuum, and the investigation of probe-size effects. Active microrheology is described starting from microscopic equations of motion for the whole system including both the host-fluid particles and the tracer; the many-body Smoluchowski equation for the case of colloidal suspensions. At low fluid densities, this can be simplified to a two-particle equation that allows the calculation of the friction coefficient with the input of the density distribution around the tracer, as shown by Brady and coworkers. The results need to be upscaled to agree with simulations at moderate density, in both the case of pulling the tracer with a constant force or dragging it at a constant velocity. The full many-particle equation has been tackled by Fuchs and coworkers, using a mode-coupling approximation and the scheme of integration through transients, valid at high densities. A localization transition is predicted for a probe embedded in a glass-forming host suspension. The

  1. Colloid filtration theory and the Happel sphere-in-cell model revisited with direct numerical simulation of colloids.

    Science.gov (United States)

    Nelson, Kirk E; Ginn, Timothy R

    2005-03-15

    The transport of colloids and bacterial cells through saturated porous media is a complex phenomenon involving many interrelated processes that are often treated via application of classical colloid filtration theory (CFT). This paper presents a numerical investigation of CFT from the Lagrangian perspective, to evaluate the role of some of the classical assumptions underlying the theory and to demonstrate a means to include processes relevant to bacterial transport that were inadequately characterized or neglected in the original formulation, including Brownian diffusion and potentially hysteretic potential functions. The methodology is based on conducting a Lagrangian trajectory analysis within Happel's sphere-in-cell porous media model to obtain the collection efficiency (eta), the frequency at which colloids or bacteria make contact with the solid phase of the porous medium. The Lagrangian framework of our model lends itself to mechanistic modeling of the biological processes that may be important in subsurface bacterial transport. The numerical study presented here focuses on the size range of bacterial colloids and smaller (down to 10 nm). Results of our model runs are in good agreement with the deterministic trajectory analysis of Rajagopalan and Tien (when diffusion is neglected) and in excellent agreement with the analytical solution to the Smoluchowski-Levich approximation of the convective-diffusion equation (when external forces and interception are neglected). Simple addition of our result for the deterministic eta to our result for the Smoluchowski-Levich eta matches the overall Rajagopalan and Tien eta to within 5% error or less for all cases studied. When we simulate diffusion and the deterministic forces together, our results diverge from the Rajagopalan and Tien eta as the particle size decreases, with discrepancies as large as 73%. These results suggest that accurate prediction of eta values for bacteria-sized (and all submicrometer) colloids

  2. Novel PLA-Based Conductive Polymer Composites for Biomedical Applications

    Science.gov (United States)

    Shah, Aziurah Mohd; Kadir, Mohammed Rafiq Abdul; Razak, Saiful Izwan Abd

    2017-12-01

    In this study, the electrical conductivity of polylactic acid (PLA)-based composites has been improved using polyaniline (PANI) with two different solvents: dodecylbenzene sulfonic acid and citric acid. The effects of various factors including PLA quantity, solvent concentration, type of solvent and thickness on the resistivity were investigated using the design of experiments. The experimental plan was based on irregular fraction design to develop the regression models. The results revealed that the proposed mathematical models were sufficient and could describe the performance of resistivity of PLA within the limits of a factor. The findings also indicated that thickness had the most significant effect on the resistivity of PLA, while the effect of the type of solvent was of least significance. Moreover, it was illustrated that, by incorporating two different solvents into PANI, the resistivity could be changed for further applications.

  3. Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media.

    Science.gov (United States)

    Kanti Sen, Tushar; Khilar, Kartic C

    2006-02-28

    In this review article, the authors present up-to-date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment/plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here the authors first present the compilation on in situ colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role in inorganic and organic contaminants transport in porous media. The important aspects of this article are as follows: (i) it gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviews the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon also depends on various factors such as concentration of colloidal fines, superficial velocity and bead-to-particle size ratio. This plugging-based contaminant transport can be used to develop containment technique in soil and groundwater remediation. (ii) It also presents the importance of critical salt concentration (CSC), critical ionic strength for mixed salt, critical shear stressor critical particle concentration (CPC) on in situ colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) It also reviews another class of colloidal fines called biocolloids and their transport in porous media. Finally, the authors highlight the future research based on their critical review on colloid-associated contaminant transport in saturated porous media.

  4. Cotransport of bismerthiazol and montmorillonite colloids in saturated porous media

    Science.gov (United States)

    Shen, Chongyang; Wang, Hong; Lazouskaya, Volha; Du, Yichun; Lu, Weilan; Wu, Junxue; Zhang, Hongyan; Huang, Yuanfang

    2015-06-01

    While bismerthiazol [N,N‧-methylene-bis-(2-amino-5-mercapto-1,3,4-thiadiazole)] is one of the most widely used bactericides, the transport of bismerthiazol in subsurface environments is unclear to date. Moreover, natural colloids are ubiquitous in the subsurface environments. The cotransport of bismerthiazol and natural colloids has not been investigated. This study conducted laboratory column experiments to examine the transport of bismerthiazol in saturated sand porous media both in the absence and presence of montmorillonite colloids. Results show that a fraction of bismerthiazol was retained in sand and the retention was higher at pH 7 than at pH 4 and 10. The retention did not change with ionic strength. The retention was attributed to the complex of bismerthiazol with metals/metal oxides on sand surfaces through ligand exchange. The transport of bismerthiazol was enhanced with montmorillonite colloids copresent in the solutions and, concurrently, the transport of montmorillonite colloids was facilitated by the bismerthiazol. The transport of montmorillonite colloids was enhanced likely because the bismerthiazol and the colloids competed for the attachment/adsorption sites on collector surfaces and the presence of bismerthiazol changed the Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energies between colloids and collectors. The transport of bismerthiazol was inhibited if montmorillonite colloids were pre-deposited in sand because bismerthiazol could adsorb onto the colloid surfaces. The adsorbed bismerthiazol could be co-remobilized with the colloids from primary minima by decreasing ionic strength. Whereas colloid-facilitated transport of pesticides has been emphasized, our study implies that transport of colloids could also be facilitated by the presence of pesticides.

  5. THE COLLOIDAL BEHAVIOR OF EDESTIN

    Science.gov (United States)

    Hitchcock, David I.

    1922-01-01

    1. It has been shown by titration experiments that the globulin edestin behaves like an amphoteric electrolyte, reacting stoichiometrically with acids and bases. 2. The potential difference developed between a solution of edestin chloride or acetate separated by a collodion membrane from an acid solution free from protein was found to be influenced by salt concentration and hydrogen ion concentration in the way predicted by Donnan's theory of membrane equilibrium. 3. The osmotic pressure of such edestin-acid salt solutions was found to be influenced by salt concentration and by hydrogen ion concentration in the same way as is the potential difference. 4. The colloidal behavior of edestin is thus completely analogous to that observed by Loeb with gelatin, casein, and egg albumin, and may be explained by Loeb's theory of colloidal behavior, which is based on the idea that proteins react stoichiometrically as amphoteric electrolytes and on Donnan's theory of membrane equilibrium. PMID:19871959

  6. Colloidal Plasmas: Basic physics of colloidal plasmas

    Indian Academy of Sciences (India)

    The present contribution will review the basic physics of the charging mechanism of the colloidal particles as well as the physics of the collective normal mode behavior of the general multi-ion species plasmas. Emphasis will be laid on the clarification of the prevailing confusing ideas about distinct qualities of the various ...

  7. Saturated Zone Colloid Transport

    Energy Technology Data Exchange (ETDEWEB)

    H. S. Viswanathan

    2004-10-07

    This scientific analysis provides retardation factors for colloids transporting in the saturated zone (SZ) and the unsaturated zone (UZ). These retardation factors represent the reversible chemical and physical filtration of colloids in the SZ. The value of the colloid retardation factor, R{sub col} is dependent on several factors, such as colloid size, colloid type, and geochemical conditions (e.g., pH, Eh, and ionic strength). These factors are folded into the distributions of R{sub col} that have been developed from field and experimental data collected under varying geochemical conditions with different colloid types and sizes. Attachment rate constants, k{sub att}, and detachment rate constants, k{sub det}, of colloids to the fracture surface have been measured for the fractured volcanics, and separate R{sub col} uncertainty distributions have been developed for attachment and detachment to clastic material and mineral grains in the alluvium. Radionuclides such as plutonium and americium sorb mostly (90 to 99 percent) irreversibly to colloids (BSC 2004 [DIRS 170025], Section 6.3.3.2). The colloid retardation factors developed in this analysis are needed to simulate the transport of radionuclides that are irreversibly sorbed onto colloids; this transport is discussed in the model report ''Site-Scale Saturated Zone Transport'' (BSC 2004 [DIRS 170036]). Although it is not exclusive to any particular radionuclide release scenario, this scientific analysis especially addresses those scenarios pertaining to evidence from waste-degradation experiments, which indicate that plutonium and americium may be irreversibly attached to colloids for the time scales of interest. A section of this report will also discuss the validity of using microspheres as analogs to colloids in some of the lab and field experiments used to obtain the colloid retardation factors. In addition, a small fraction of colloids travels with the groundwater without any significant

  8. Study on alkyd-based electrically conductive coatings

    Energy Technology Data Exchange (ETDEWEB)

    Du Zhiming; Cong Xiaomin; Wang Peng [State Key Lab. of the Prevention and Control of Explosion Disasters, Beijing Inst. of Tech., Beijing, BJ (China)

    2005-07-01

    Carbonaceous fillers have been widely applied in electrically conductive coatings due to their cheaper, steady electrically conductive capability and other excellent performances. Electrically conductive coatings were synthesized by using graphite and carbon black as fillers in the alkyd resin matrices. Influences of various fillers on electrical conductivity of coatings have been investigated in detail. (orig.)

  9. Explorative analysis of microbes, colloids and gases

    International Nuclear Information System (INIS)

    Hallbeck, Lotta; Pedersen, Karsten

    2008-08-01

    The overall objectives of the hydrogeochemical description for Forsmark are to establish a detailed understanding of the hydrogeochemical conditions at the site and to develop models that fulfil the needs identified by the safety assessment groups during the site investigation phase. Issues of concern to safety assessment are radionuclide transport and technical barrier behaviour, both of which are dependent on the chemistry of groundwater and pore water and their evolution with time. In this report, part of the final hydrogeochemical evaluation work of the site investigation at the Forsmark site, is presented. The work was conducted by SKB's hydrogeochemical project group, ChemNet, which consists of independent consultants and Univ. researchers with expertise in geochemistry, hydrochemistry, hydrogeochemistry, microbiology, geomicrobiology, analytical chemistry etc. The resulting site descriptive model version, mainly based on 2.2 data and complementary 2.3 data, was carried out during September 2006 to December 2007. This report focuses on microbiology, colloids and gases: - Microbes (Chapter 1): Several methods must be used to characterize active microbial communities in groundwater. Microbial parameters of interest are the total number of cells (TNC) and the presence of various metabolic groups of microorganisms. Different microbial groups influence the environment in different ways, depending on what metabolic group is dominant. Typically, the following redox couples are utilized by bacteria in granitic groundwater: H 2 O/O 2 , NO 3 - /N 2 , Mn 2+ /Mn(IV), Fe 2+ /Fe(III), S 2- /SO 4 2- , CH 4 /CO 2 , CH 3 COOH/CO 2 , and H 2 /H + . The data will indicate the activity of specific microbial populations at particular sites and how they may affect the geochemistry. - Colloids (Chapter 2): Particles in the size range from 1 to 1x10 -3 μm are regarded as colloids. Their small size prohibits them from settling, which gives them the potential to transport

  10. Explorative analysis of microbes, colloids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Hallbeck, Lotta; Pedersen, Karsten (Microbial Analytics Sweden AB, Goeteborg (Sweden))

    2008-08-15

    The overall objectives of the hydrogeochemical description for Forsmark are to establish a detailed understanding of the hydrogeochemical conditions at the site and to develop models that fulfil the needs identified by the safety assessment groups during the site investigation phase. Issues of concern to safety assessment are radionuclide transport and technical barrier behaviour, both of which are dependent on the chemistry of groundwater and pore water and their evolution with time. In this report, part of the final hydrogeochemical evaluation work of the site investigation at the Forsmark site, is presented. The work was conducted by SKB's hydrogeochemical project group, ChemNet, which consists of independent consultants and Univ. researchers with expertise in geochemistry, hydrochemistry, hydrogeochemistry, microbiology, geomicrobiology, analytical chemistry etc. The resulting site descriptive model version, mainly based on 2.2 data and complementary 2.3 data, was carried out during September 2006 to December 2007. This report focuses on microbiology, colloids and gases: - Microbes (Chapter 1): Several methods must be used to characterize active microbial communities in groundwater. Microbial parameters of interest are the total number of cells (TNC) and the presence of various metabolic groups of microorganisms. Different microbial groups influence the environment in different ways, depending on what metabolic group is dominant. Typically, the following redox couples are utilized by bacteria in granitic groundwater: H{sub 2}O/O{sub 2}, NO{sub 3}-/N{sub 2}, Mn2+/Mn(IV), Fe2+/Fe(III), S2-/SO{sub 4}2-, CH{sub 4}/CO{sub 2}, CH{sub 3}COOH/CO{sub 2}, and H{sub 2}/H+. The data will indicate the activity of specific microbial populations at particular sites and how they may affect the geochemistry. - Colloids (Chapter 2): Particles in the size range from 1 to 1x10-3 mum are regarded as colloids. Their small size prohibits them from settling, which gives them the

  11. Forming mechanism of Te-based conductive-bridge memories

    Science.gov (United States)

    Mendes, M. Kazar; Martinez, E.; Marty, A.; Veillerot, M.; Yamashita, Y.; Gassilloud, R.; Bernard, M.; Renault, O.; Barrett, N.

    2018-02-01

    We investigated origins of the resistivity change during the forming of ZrTe/Al2O3 based conductive-bridge resistive random access memories. Non-destructive hard X-ray photoelectron spectroscopy was used to investigate redox processes with sufficient depth sensitivity. Results highlighted the reduction of alumina correlated to the oxidation of zirconium at the interface between the solid electrolyte and the active electrode. In addition the resistance switching caused a decrease of Zr-Te bonds and an increase of elemental Te showing an enrichment of tellurium at the ZrTe/Al2O3 interface. XPS depth profiling using argon clusters ion beam confirmed the oxygen diffusion towards the top electrode. A four-layer capacitor model showed an increase of both the ZrO2 and AlOx interfacial layers, confirming the redox process located at the ZrTe/Al2O3 interface. Oxygen vacancies created in the alumina help the filament formation by acting as preferential conductive paths. This study provides a first direct evidence of the physico-chemical phenomena involved in resistive switching of such devices.

  12. Electrochemical DNA Hybridization Sensors Based on Conducting Polymers

    Science.gov (United States)

    Rahman, Md. Mahbubur; Li, Xiao-Bo; Lopa, Nasrin Siraj; Ahn, Sang Jung; Lee, Jae-Joon

    2015-01-01

    Conducting polymers (CPs) are a group of polymeric materials that have attracted considerable attention because of their unique electronic, chemical, and biochemical properties. This is reflected in their use in a wide range of potential applications, including light-emitting diodes, anti-static coating, electrochromic materials, solar cells, chemical sensors, biosensors, and drug-release systems. Electrochemical DNA sensors based on CPs can be used in numerous areas related to human health. This review summarizes the recent progress made in the development and use of CP-based electrochemical DNA hybridization sensors. We discuss the distinct properties of CPs with respect to their use in the immobilization of probe DNA on electrode surfaces, and we describe the immobilization techniques used for developing DNA hybridization sensors together with the various transduction methods employed. In the concluding part of this review, we present some of the challenges faced in the use of CP-based DNA hybridization sensors, as well as a future perspective. PMID:25664436

  13. All-solid-state reference electrodes based on conducting polymers.

    Science.gov (United States)

    Kisiel, Anna; Marcisz, Honorata; Michalska, Agata; Maksymiuk, Krzysztof

    2005-12-01

    A novel construction of solution free (pseudo)reference electrodes, compatible with all-solid-state potentiometric indicator electrodes, has been proposed. These electrodes use conducting polymers (CP): polypyrrole (PPy) or poly(3,4-ethylenedioxythiophene) (PEDOT). Two different arrangements have been tested: solely based on CP and those where the CP phase is covered with a poly(vinyl chloride) based outer membrane of tailored composition. The former arrangement was designed to suppress or compensate cation- and anion-exchange, using mobile perchlorate ions and poly(4-styrenesulfonate) or dodecylbenzenesulfonate anions as immobilized dopants. The following systems were used: (i) polypyrrole layers doped simultaneously by two kinds of anions, both mobile and immobilized in the polymer layer; (ii) bilayers of polypyrrole with anion exchanging inner layer and cation-exchanging outer layer; (iii) polypyrrole doped by surfactant dodecylbenzenesulfonate ions, which inhibit ion exchange on the polymer/solution interface. For the above systems, recorded potentials have been found to be practically independent of electrolyte concentration. The best results, profound stability of potentials, have been obtained for poly(3,4-ethylenedioxythiophene) or polypyrrole doped by poly(4-styrenesulfonate) anions covered by a poly(vinyl chloride) based membrane, containing both anion- and cation-exchangers as well as solid potassium chloride and silver chloride with metallic silver. Differently to the cases (i)-(iii) these electrodes are much less sensitive to the influence of redox and pH interferences. This arrangement has been also characterized using electrochemical impedance spectroscopy and chronopotentiometry.

  14. Electrochemical DNA Hybridization Sensors Based on Conducting Polymers

    Directory of Open Access Journals (Sweden)

    Md. Mahbubur Rahman

    2015-02-01

    Full Text Available Conducting polymers (CPs are a group of polymeric materials that have attracted considerable attention because of their unique electronic, chemical, and biochemical properties. This is reflected in their use in a wide range of potential applications, including light-emitting diodes, anti-static coating, electrochromic materials, solar cells, chemical sensors, biosensors, and drug-release systems. Electrochemical DNA sensors based on CPs can be used in numerous areas related to human health. This review summarizes the recent progress made in the development and use of CP-based electrochemical DNA hybridization sensors. We discuss the distinct properties of CPs with respect to their use in the immobilization of probe DNA on electrode surfaces, and we describe the immobilization techniques used for developing DNA hybridization sensors together with the various transduction methods employed. In the concluding part of this review, we present some of the challenges faced in the use of CP-based DNA hybridization sensors, as well as a future perspective.

  15. Colloids in Biotechnology

    CERN Document Server

    Fanun, Monzer

    2010-01-01

    Colloids have come a long way from when Thomas Graham coined the term colloid to describe 'pseudo solutions'. This book enables scientists to close the gap between extensive research and translation into commercial options in biomedicine and biotechnology. It covers biosurfactants and surface properties, phase behavior, and orientational change of surfactant mixtures with peptides at the interface. It also covers adsorption of polymers and biopolymers on the surface and interface, discusses colloidal nanoparticles and their use in biotechnology, and delves into bioadhesion and microencapsulati

  16. Statistical Physics of Colloidal Dispersions.

    Science.gov (United States)

    Canessa, E.

    Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the equilibrium statistical mechanics of colloidal dispersions which represent useful model systems for the study of condensed matter physics; namely, charge stabilized colloidal dispersions and polymer stabilized colloidal dispersions. A one-component macroparticle approach is adopted in order to treat the macroscopic and microscopic properties of these systems in a simple and comprehensive manner. The thesis opens with the description of the nature of the colloidal state before reviewing some basic definitions and theory in Chapter II. In Chapter III a variational theory of phase equilibria based on the Gibbs-Bogolyobov inequality is applied to sterically stabilized colloidal dispersions. Hard spheres are chosen as the reference system for the disordered phases while an Einstein model is used for the ordered phases. The new choice of pair potential, taken for mathematical convenience, is a superposition of two Yukawa functions. By matching a double Yukawa potential to the van der Waals attractive potential at different temperatures and introducing a purely temperature dependent coefficient to the repulsive part, a rich variety of observed phase separation phenomena is qualitatively described. The behaviour of the potential is found to be consistent with a small decrease of the polymer layer thickness with increasing temperature. Using the same concept of a collapse transition the non-monotonic second virial coefficient is also explained and quantified. It is shown that a reduction of the effective macroparticle diameter with increasing temperature can only be partially examined from the point of view of a (binary-) polymer solution theory. This chapter concludes with the description of the observed, reversible, depletion flocculation behaviour. This is accomplished by using the variational formalism and by invoking the double Yukawa potential to allow

  17. Shape Separation of Colloidal Metal Nanoparticles via Size Exclusion Chromatography

    OpenAIRE

    Marvi, Sarrah

    2016-01-01

    The inherent polydispersity of solution-based, colloidal nanoparticle syntheses has necessitated the development of facile post-processing methods for the purification of anisotropic nanoparticles. Here, the use of size exclusion chromatography is explored for the shape separation of colloidal silver nanocube and colloidal gold bipyramid solutions. Multiple column packing materials, pore sizes, and mobile phases were tested to address the prevalent issues of metal adsorption to the high surfa...

  18. Colloids dragged through a polymer solution: experiment, theory and simulation

    OpenAIRE

    Gutsche, Christof; Kremer, Friedrich; Krüger, Matthias; Rauscher, Markus; Weeber, Rudolf; Harting, Jens

    2007-01-01

    We present micro-rheological measurments of the drag force on colloids pulled through a solution of lambda-DNA (used here as a monodisperse model polymer) with an optical tweezer. The experiments show a violation of the Stokes-Einstein relation based on the independently measured viscosity of the DNA solution: the drag force is larger than expected. We attribute this to the accumulation of DNA infront of the colloid and the reduced DNA density behind the colloid. This hypothesis is corroborat...

  19. Colloids or artefacts?

    International Nuclear Information System (INIS)

    Laaksoharju, M.; Vuorinen, U.; Allard, B.; Pettersson, C.; Hinkkanen, H.

    1994-01-01

    TVO (Teollisuuden Voima Oy, Finland) initiated a co-operative task with SKB (Swedish Nuclear Fuel and Waste Management Co.) to critically evaluate colloid sampling methods at the test site in Olkiluoto, SW Finland. Three different colloid sampling methods were compared when sampling at 613-618 m depth. The colloid sampling consisted of ordinary filtering (cross-flow filtering, 20-450 nm) in open air, inert filtering (cross-flow filtering, prefilter=2500 nm, separate filtration to three fractions 50,200 and 400 nm) by using N 2 and ultrafiltration (tangential filtering, prefilter=1000 nm concentration to a single fraction 2-1000 nm) using N 2 . Two samples per method were taken with an interval of three weeks. For organic determination one sample was collected. Care was taken to avoid possible known artefacts in connection with the colloid sampling. (27 refs., 31 figs., 13 tabs.)

  20. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  1. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    International Nuclear Information System (INIS)

    Krishnan, V.B.; Singh, J.D.; Woodruff, T.R.; Vaidyanathan, R.; Notardonato, W.U.

    2004-01-01

    Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed

  2. Some physical properties of Nb2O5 thin films prepared using nobic acid based colloidal suspension at room temperature

    Science.gov (United States)

    Salim, Evan T.; Admon Saimon, Jehan; Abood, Marwa K.; Fakhri, Makram A.

    2017-10-01

    This work presents the successful preparation of niobium pentoxide micro structures thin films at room temperature. A chemical colloidal suspension was deposited employing Spin coating method. Nb2O5 thin films were prepared at two different thicknesses before and after ultrasonic vibration processes. Optical, structural, and morphological properties were studied. An enhanced crystalline structure with bigger grain size at both thicknesses was obtained after ultrasonic process; this was ensured by SEM results. The energy gap of the prepared films was estimated and found to be about (2.81, 2.42) eV for (T1  =  325 nm) and (2.59, 2.32) eV at the second thickness (T2  =  425 nm). The I-V characteristic study of prepared heterojunction on silicon substrate show an increase in the rectification ratio after the ultrasonic vibrational process for both thicknesses.

  3. Role of air-water interfaces in colloid transport in porous media: A review

    Science.gov (United States)

    Flury, Markus; Aramrak, Surachet

    2017-07-01

    Air-water interfaces play an important role in unsaturated porous media, giving rise to phenomena like capillarity. Less recognized and understood are interactions of colloids with the air-water interface in porous media and the implications of these interactions for fate and transport of colloids. In this review, we discuss how colloids, both suspended in the aqueous phase and attached at pore walls, interact with air-water interfaces in porous media. We discuss the theory of colloid/air-water interface interactions, based on the different forces acting between colloids and the air-water interface (DLVO, hydrophobic, capillary forces) and based on thermodynamic considerations (Gibbs free energy). Subsurface colloids are usually electrostatically repelled from the air-water interface because most subsurface colloids and the air-water are negatively charged. However, hydrophobic interactions can lead to attraction to the air-water interface. When colloids are at the air-water interface, capillary forces are usually dominant over other forces. Moving air-water interfaces are effective in mobilizing and transporting colloids from surfaces. Thermodynamic considerations show that, for a colloid, the air-water interface is the favored state as compared with the suspension phase, except for hydrophilic colloids in the nanometer size range. Experimental evidence indicates that colloid mobilization in soils often occurs through macropores, although matrix transport is also prevalent in absence of macropores. Moving air-water interfaces, e.g., occurring during infiltration, imbibition, or drainage, have been shown to scour colloids from surfaces and translocate colloids. Colloids can also be pinned to surfaces by thin water films and capillary menisci at the air-water-solid interface line, causing colloid retention and immobilization. Air-water interfaces thus can both mobilize or immobilize colloids in porous media, depending on hydrodynamics and colloid and surface

  4. Parameter and model sensitivities for colloid-facilitated radionuclide transport on the field scale

    Science.gov (United States)

    Cvetkovic, V.; Painter, S.; Turner, D.; Pickett, D.; Bertetti, P.

    2004-06-01

    We investigate the potential effects of inorganic colloids on radionuclide transport in groundwater using generic sensitivity studies and an example based on the alluvial aquifer near Yucca Mountain, Nevada. Our emphasis is on kinetically controlled sorption of radionuclides on mobile and immobile colloids. Three kinetic sorption models are considered for the sensitivity analysis: bilinear, Langmuir, and linear. Plutonium is assumed to be injected into the Yucca Mountain alluvial aquifer at a constant rate and follows a random stream tube to a monitoring boundary. The linear sorption model provides a reasonable upper bound on colloid-facilitated plutonium transport for the site-specific conditions. In the absence of colloid filtration and retardation, colloids enhance the plutonium discharge by a large factor over the situation without colloids. Exchange of plutonium between solution and reversibly attached colloids makes colloid retardation relatively ineffective at reducing colloid-facilitated transport except when the retardation factor is large. Irreversible removal of colloids (filtration) is more effective than retardation at reducing colloid-facilitated transport. For fixed filtration rate the degree of attenuation depends sensitively and nonmonotonically on the rate of plutonium desorption from colloids. These results emphasize the need for accurate measurements of rates of desorption from colloids as well as in situ studies of filtration of naturally occurring colloids.

  5. Structural and conductivity changes during the pyrolysis of polyaniline base

    Czech Academy of Sciences Publication Activity Database

    Trchová, Miroslava; Matějka, P.; Brodinová, J.; Kalendová, A.; Prokeš, J.; Stejskal, Jaroslav

    2006-01-01

    Roč. 91, č. 1 (2006), s. 114-121 ISSN 0141-3910 R&D Projects: GA AV ČR IAA4050313; GA AV ČR IAA400500504 Institutional research plan: CEZ:AV0Z40500505 Keywords : polyaniline * conducting polymer * conductivity Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.174, year: 2006

  6. Conductivity modeling of gas sensors based on copper ...

    African Journals Online (AJOL)

    The main objective of this work is to study the electronic conductivity of copper phthalocyanine (CuPc) thin films in presence of certain strong oxidizing gases involved in air pollution, particularly NO2, for use as gas sensor devices. To achieve this objective, the first part presents a study of the conductivity evolution of these ...

  7. RF Shimming improves Phase-based Conductivity Imaging

    NARCIS (Netherlands)

    Katscher, U.; Van Lier, A.L.H.M.W.; Van den Berg, C.A.T.; Keupp, J.

    2012-01-01

    In the framework of “Electric Properties Tomography” (EPT), approximate conductivity imaging is possible by analyzing the B1 phase, assuming constant B1 amplitude. The more this assumption is violated, the less accurate the reconstructed conductivity. This study optimizesthe B1 amplitude via

  8. Conductivity study of solid polyelectrolytes based on hydroiodide ...

    Indian Academy of Sciences (India)

    It was evidenced by the fact that conductivity measurement made on the solid charge transfer (CT) complex formed between P-4VP and iodine showed no ionic conduction because of the loss of polar cha- racter of the polymeric backbone due to the involvement of lone pair of electrons on nitrogen atom in CT complex for-.

  9. Actinide colloid generation in groundwater

    International Nuclear Information System (INIS)

    Kim, J.I.

    1990-05-01

    The progress made in the investigation of actinide colloid generation in groundwaters is summarized and discussed with particular examples relevant to an understanding of the migration behaviour of actinides in natural aquifer systems. The first part deals with the characterization of colloids: groundwater colloids, actinide real-colloids and actinide pseudocolloids. The second part concentrates on the generation processes and migration behaviour of actinide pseudocolloids, which are discussed with some notable experimental examples. Importance is stressed more on the chemical aspects of the actinide colloid generation in groundwater. This work is a contribution to the CEC project MIRAGE II, particularly, to research area: complexation and colloids. (orig.)

  10. Effects of Cholesterol Incorporation on the Physicochemical, Colloidal, and Biological Characteristics of pH-sensitive AB2 Miktoarm Polymer-Based Polymersomes

    Science.gov (United States)

    Yin, Haiqing; Kang, Han Chang; Huh, Kang Moo; Bae, You Han

    2014-01-01

    In our previous study, a histidine-based AB2 miktoarm polymer, methoxy poly(ethylene glycol)-b-poly(l-histidine)2 (mPEG-b-(PolyHis)2), was designed to construct pH-sensitive polymersomes that transform in acidic pH; the polymer self-assembles into a structure that mimics phospholipids. In this study, the polymersomes further imitated liposomes due to the incorporation of cholesterol (CL). The hydrodynamic radii of the polymersomes increased with increasing CL wt% (e.g., 70 nm for 0 wt% vs. 91 nm for 1 wt%), resulting in an increased capacity for encapsulating hydrophilic drugs (e.g., 0.92 µL/mg for 0 wt% vs. 1.42 µL/mg for 1 wt%). The CL incorporation enhanced the colloidal stability of the polymersomes in the presence of serum protein and retarded their payload release. However, CL-incorporating polymersomes still demonstrated accelerated release of a hydrophilic dye (e.g., 5(6)-carboxyfluorescein (CF)) below pH 6.8 without losing their desirable pH sensitivity. CF-loaded CL-incorporating polymersomes showed better cellular internalization than the hydrophilic CF, whereas doxorubicin (DOX)-loaded CL-incorporating polymersomes presented similar or somewhat lower anti-tumor effects than free hydrophobic DOX. The findings suggest that CL-incorporating mPEG-b-(PolyHis)2-based polymersomes may have potential for intracellular drug delivery of chemical drugs due to their improved colloidal stability, lower drug loss during circulation, acidic pH-induced drug release, and endosomal disruption. PMID:24463148

  11. Conductance of graphene-based double-barrier nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Setare, M R [Department of Campus of Bijar, University of Kurdistan, Bijar (Iran, Islamic Republic of); Jahani, D, E-mail: Rezakord@ipm.co, E-mail: Dariush110@gmail.co [Department of Physics, Razi University, Kermanshah (Iran, Islamic Republic of)

    2010-12-22

    The effect of a mass gap on the conductance of graphene double-barrier heterojunctions is studied. By obtaining the 2D expression for the electronic transport of the low energy excitations of pure graphene through double-barrier systems, it is found that the conductivity of these structures does not depend on the type of charge carriers in the zones of the electric field. However, a finite induced gap in the graphene spectrum makes conductivity dependent on the energy band index. We also discuss a few controversies concerning double-barrier systems stemming from an improper choice of the scattering angle. Then it is observed that, for some special values of the incident energy and potential's height, graphene junctions behave like left-handed materials, resulting in a maximum value for the conductivity.

  12. Current Trends in Sensors Based on Conducting Polymer Nanomaterials

    Science.gov (United States)

    Yoon, Hyeonseok

    2013-01-01

    Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials through synthesis methods such as solid-phase template synthesis, molecular template synthesis, and template-free synthesis. Nanostructured conducting polymers featuring high surface area, small dimensions, and unique physical properties have been widely used to build various sensor devices. Many remarkable examples have been reported over the past decade. The enhanced sensitivity of conducting polymer nanomaterials toward various chemical/biological species and external stimuli has made them ideal candidates for incorporation into the design of sensors. However, the selectivity and stability still leave room for improvement. PMID:28348348

  13. Graphene Based Terahertz Absorber Designed With Effective Surface Conductivity Approach

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Pizzocchero, Filippo; Booth, Tim

    is flexible and ultrastrong mechanically, transparent for optical radiation, with high electrical conductivity that can be tuned by electrochemical potential. Structured graphene layers constitute metamaterials that can provide tunable and very unusual electromagnetic properties. In this contribution we...... present the description of graphene metamaterial properties through the effective surface conductivity. Such description is very convenient, as it simplifies the design of THz devices, and very natural, since surface conductivity can be measured directly in experiment. We show how to extract the effective...... conductivity and how to use it in optical design. We demonstrate a tunable THz perfect absorber, which consists of continuous graphene various structured graphene metamaterials above a metal mirror. Changing the Fermi level from 0 eV to 0.5 eV allows for drastic changes in absorbance from less than 0.1 to 1...

  14. Current Trends in Sensors Based on Conducting Polymer Nanomaterials

    Directory of Open Access Journals (Sweden)

    Hyeonseok Yoon

    2013-08-01

    Full Text Available Conducting polymers represent an important class of functional organic materials for next-generation electronic and optical devices. Advances in nanotechnology allow for the fabrication of various conducting polymer nanomaterials through synthesis methods such as solid-phase template synthesis, molecular template synthesis, and template-free synthesis. Nanostructured conducting polymers featuring high surface area, small dimensions, and unique physical properties have been widely used to build various sensor devices. Many remarkable examples have been reported over the past decade. The enhanced sensitivity of conducting polymer nanomaterials toward various chemical/biological species and external stimuli has made them ideal candidates for incorporation into the design of sensors. However, the selectivity and stability still leave room for improvement.

  15. Ionic conductivity and diffusion coefficient of barium-chloride-based ...

    Indian Academy of Sciences (India)

    styrenesulphonic acid) with bariumchloride dihydrate (BaCl 2 ·2H 2 O) salt complex has been synthesized following the usual solution casting. The ionic conductivity of polymer electrolyte was analysed by impedance spectroscopy. The highest room ...

  16. A Field-Based Aquatic Life Benchmark for Conductivity in ...

    Science.gov (United States)

    This report adapts the standard U.S. EPA methodology for deriving ambient water quality criteria. Rather than use toxicity test results, the adaptation uses field data to determine the loss of 5% of genera from streams. The method is applied to derive effect benchmarks for dissolved salts as measured by conductivity in Central Appalachian streams using data from West Virginia and Kentucky. This report provides scientific evidence for a conductivity benchmark in a specific region rather than for the entire United States.

  17. Effective Surface Conductivity Approach for Graphene Metamaterials Based Terahertz Devices

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Pizzocchero, Filippo; Booth, Tim

    2013-01-01

    We propose a description of graphene metamaterials properties through the effective surface conductivity. On the example of tunable absorber we demonstrate that this approach allows for fast and efficient design of functional terahertz devices.......We propose a description of graphene metamaterials properties through the effective surface conductivity. On the example of tunable absorber we demonstrate that this approach allows for fast and efficient design of functional terahertz devices....

  18. Conductance-based profiling of nanopores: Accommodating fabrication irregularities.

    Science.gov (United States)

    Bandara, Y M N D Y; Nichols, Jonathan W; Iroshika Karawdeniya, Buddini; Dwyer, Jason R

    2018-02-01

    Solid-state nanopores are nanoscale channels through otherwise impermeable membranes. Single molecules or particles can be passed through electrolyte-filled nanopores by, e.g. electrophoresis, and then detected through the resulting physical displacement of ions within the nanopore. Nanopore size, shape, and surface chemistry must be carefully controlled, and on extremely challenging nanopores from the time-dependent changes in their conductance as they are being formed through solution-phase nanofabrication processes with the appeal of ease and accessibility. We revisited this simulation work, confirmed the suitability of the basic conductance equation using the results of time-dependent experimental conductance measurements during nanopore fabrication by Yanagi et al., and then deliberately relaxed the model constraints to allow for (i) the presence of defects; and (ii) the formation of two small pores instead of one larger one. Our simulations demonstrated that the time-dependent conductance formalism supports the detection and characterization of defects, as well as the determination of pore number, but with implementation performance depending on the measurement context and results. In some cases, the ability to discriminate numerically between the correct and incorrect nanopore profiles was slight, but with accompanying differences in candidate nanopore dimensions that could yield to post-fabrication conductance profiling, or be used as convenient uncertainty bounds. Time-dependent nanopore conductance thus offers insight into nanopore structure and function, even in the presence of fabrication defects. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Infrared colloidal lead chalcogenide nanocrystals: synthesis, properties, and photovoltaic applications.

    Science.gov (United States)

    Fu, Huiying; Tsang, Sai-Wing

    2012-04-07

    Simple solution phase, catalyst-free synthetic approaches that offer monodispersed, well passivated, and non-aggregated colloidal semiconductor nanocrystals have presented many research opportunities not only for fundamental science but also for technological applications. The ability to tune the electrical and optical properties of semiconductor nanocrystals by manipulating the size and shape of the crystals during the colloidal synthesis provides potential benefits to a variety of applications including photovoltaic devices, light-emitting diodes, field effect transistors, biological imaging/labeling, and more. Recent advances in the synthesis and characterization of colloidal lead chalcogenide nanocrystals and the achievements in colloidal PbS or PbSe nanocrystals solar cells have demonstrated the promising application of infrared-emitting colloidal lead chalcogenide nanocrystals in photovoltaic devices. Here, we review recent progress in the synthesis and optical properties of colloidal lead chalcogenide nanocrystals. We focus in particular upon the size- and shape-controlled synthesis of PbS, PbSe, and PbTe nanocrystals by using different precursors and various stabilizing surfactants for the growth of the colloidal nanocrystals. We also summarize recent advancements in the field of colloidal nanocrystals solar cells based on colloidal PbS and PbSe nanocrystals. This journal is © The Royal Society of Chemistry 2012

  20. Infrared colloidal lead chalcogenide nanocrystals: Synthesis, properties, and photovoltaic applications

    Science.gov (United States)

    Fu, Huiying; Tsang, Sai-Wing

    2012-03-01

    Simple solution phase, catalyst-free synthetic approaches that offer monodispersed, well passivated, and non-aggregated colloidal semiconductor nanocrystals have presented many research opportunities not only for fundamental science but also for technological applications. The ability to tune the electrical and optical properties of semiconductor nanocrystals by manipulating the size and shape of the crystals during the colloidal synthesis provides potential benefits to a variety of applications including photovoltaic devices, light-emitting diodes, field effect transistors, biological imaging/labeling, and more. Recent advances in the synthesis and characterization of colloidal lead chalcogenide nanocrystals and the achievements in colloidal PbS or PbSe nanocrystals solar cells have demonstrated the promising application of infrared-emitting colloidal lead chalcogenide nanocrystals in photovoltaic devices. Here, we review recent progress in the synthesis and optical properties of colloidal lead chalcogenide nanocrystals. We focus in particular upon the size- and shape-controlled synthesis of PbS, PbSe, and PbTe nanocrystals by using different precursors and various stabilizing surfactants for the growth of the colloidal nanocrystals. We also summarize recent advancements in the field of colloidal nanocrystals solar cells based on colloidal PbS and PbSe nanocrystals.

  1. Steady heat conduction-based thermal conductivity measurement of single walled carbon nanotubes thin film using a micropipette thermal sensor.

    Science.gov (United States)

    Shrestha, R; Lee, K M; Chang, W S; Kim, D S; Rhee, G H; Choi, T Y

    2013-03-01

    In this paper, we describe the thermal conductivity measurement of single-walled carbon nanotubes thin film using a laser point source-based steady state heat conduction method. A high precision micropipette thermal sensor fabricated with a sensing tip size varying from 2 μm to 5 μm and capable of measuring thermal fluctuation with resolution of ±0.01 K was used to measure the temperature gradient across the suspended carbon nanotubes (CNT) film with a thickness of 100 nm. We used a steady heat conduction model to correlate the temperature gradient to the thermal conductivity of the film. We measured the average thermal conductivity of CNT film as 74.3 ± 7.9 W m(-1) K(-1) at room temperature.

  2. Nematic Liquid-Crystal Colloids.

    Science.gov (United States)

    Muševič, Igor

    2017-12-25

    This article provides a concise review of a new state of colloidal matter called nematic liquid-crystal colloids. These colloids are obtained by dispersing microparticles of different shapes in a nematic liquid crystal that acts as a solvent for the dispersed particles. The microparticles induce a local deformation of the liquid crystal, which then generates topological defects and long-range forces between the neighboring particles. The colloidal forces in nematic colloids are much stronger than the forces in ordinary colloids in isotropic solvents, exceeding thousands of k B T per micrometer-sized particle. Of special interest are the topological defects in nematic colloids, which appear in many fascinating forms, such as singular points, closed loops, multitudes of interlinked and knotted loops or soliton-like structures. The richness of the topological phenomena and the possibility to design and control topological defects with laser tweezers make colloids in nematic liquid crystals an excellent playground for testing the basic theorems of topology.

  3. Nanomechanical properties of polymer brushes by colloidal AFM probes

    NARCIS (Netherlands)

    Kutnyanszky, E.; Vancso, Gyula J.

    2012-01-01

    Nanomechanical properties of end grafted polymer layers were studied by AFM based, colloidal probe compression measurements. Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) brush was grafted from planar Si surface and poly(methyl methacrylate) (PMAA) brush was grown on colloidal probe by

  4. Mesoscopic model of temporal and spatial heterogeneity in aging colloids

    DEFF Research Database (Denmark)

    Becker, Nikolaj; Sibani, Paolo; Boettcher, Stefan

    2014-01-01

    We develop a simple and effective description of the dynamics of dense hard sphere colloids in the aging regime deep in the glassy phase. Our description complements the many efforts to understand the onset of jamming in low density colloids, whose dynamics is still time-homogeneous. Based...

  5. A lateral flow colloidal gold-based immunoassay for rapid detection of miroestrol in samples of White Kwao Krua, a phytoestrogen-rich plant.

    Science.gov (United States)

    Kitisripanya, Tharita; Inyai, Chadathorn; Komaikul, Jukrapun; Krittanai, Supaluk; Juengwatanatrakul, Thaweesak; Sakamoto, Seiichi; Tanaka, Hiroyuki; Morimoto, Satoshi; Putalun, Waraporn

    2017-10-01

    White Kwao Krua (WKK)-derived products have been used worldwide as dietary supplements to relieve climacteric symptoms in menopausal women. Miroestrol is a unique chromene found in WKK tuberous roots that corresponds to the estrogenic activity of WKK. However, miroestrol naturally accumulates at low levels in WKK samples, which are difficult to detect. The development of a rapid and sensitive assay to detect miroestrol in numerous products derived from this plant would be a practical and useful method to guarantee the quality of raw materials. To allow rapid and easy qualitative detection of miroestrol, a lateral flow immunoassay (LFIA) using a colloidal gold-labeled monoclonal antibody (mAb) against miroestrol was developed. The qualitative LFIA was based on the competition of free miroestrol in the sample and immobilized miroestrol-conjugated proteins on the strip for a limited number of antibodies in the detection reagent. Anti-miroestrol mAb was colored by colloidal gold labels and used as the detection reagent in LFIA. Anti-mouse immunoglobulin G was used to indicate the functioning of the LFIA system. The detection limit of the LFIA was 0.156 μg of miroestrol. The LFIA was applied to determine the miroestrol content in WKK samples and products. The result was compared with the validated enzyme-linked immunosorbent assay (ELISA) and demonstrated a correlative outcome. This study shows that the developed LFIA is practical and suitable for detecting small amounts of miroestrol in WKK samples. This qualitative assay is more rapid in screening miroestrol in WKK samples (within 10 min) than conventional methods (ELISA and HPLC).

  6. High ionic conductivity in confined bismuth oxide-based heterostructures

    Directory of Open Access Journals (Sweden)

    Simone Sanna

    2016-12-01

    Full Text Available Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3 exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure δ-Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ, deposited by pulsed laser deposition. The resulting [δ-Bi2O3/YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C and exhibits stable high ionic conductivity over a long time comparable to the value of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk.

  7. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...... of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk....

  8. Evaluation of point-of-care analyzers' ability to reduce bias in conductivity-based hematocrit measurement during cardiopulmonary bypass.

    Science.gov (United States)

    Teerenstra, Steven; Steinfelder-Visscher, Jacoline; Gunnewiek, Jacqueline Klein; Weerwind, Patrick W

    2014-04-01

    Most point-of-care testing analyzers use the conductivity method to measure hematocrit (hct). During open-heart surgery, blood-conductivity is influenced by shifts in electrolyte and colloid concentrations caused by infusion media used, and this may lead to considerable bias in the hct measurement. We evaluated to what extent different analyzers correcting for 0, 1, 2, or 3 factors, respectively, compensated for this electrolyte/colloid interference: (1) the conductivity method with no correction (IRMA), (2) with a [Na(+)]-correction (GEM Premier 3000), (3) with a [Na(+)]/[K(+)]-correction (i-STAT), and (4) with a [Na(+)]/[K(+)]-correction in combination with an algorithm that estimates the protein dilution [i-STAT in cardiopulmonary bypass (CPB)-mode]. Bias in hct was measured during three consecutive stages of a CPB procedure: (I) before CPB, (II) start of CPB and (III) after cardioplegia. In order of high to low electrolyte/colloid interference: the analyzer with no correction, [Na(+)]-correction, [Na(+)/]/[K(+)]-correction, and [Na(+)/]/[K(+)]/estimated protein-correction showed a change of bias from stage I to stage III of -3.9 ± 0.5, -3.4 ± 0.4, -2.1 ± 0.5, -0.3 ± 0.5%. We conclude that correcting for more parameters (Na(+), K(+), estimated protein) gives less bias, but residual bias remains even after [Na(+)/]/[K(+)]/estimated protein-correction. This suggests that a satisfactory algorithm should also correct for other colloidal factors than protein.

  9. High ionic conductivity in confined bismuth oxide-based heterostructures

    DEFF Research Database (Denmark)

    Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens

    2016-01-01

    Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...

  10. Well-log based prediction of thermal conductivity

    DEFF Research Database (Denmark)

    Fuchs, Sven; Förster, Andrea

    Rock thermal conductivity (TC) is paramount for the determination of heat flow and the calculation of temperature profiles. Due to the scarcity of drill cores compared to the availability of petrophysical well logs, methods are desired to indirectly predict TC in sedimentary basins. Most of the w......Rock thermal conductivity (TC) is paramount for the determination of heat flow and the calculation of temperature profiles. Due to the scarcity of drill cores compared to the availability of petrophysical well logs, methods are desired to indirectly predict TC in sedimentary basins. Most...

  11. Effective SERS-active substrates composed of hierarchical micro/nanostructured arrays based on reactive ion etching and colloidal masks.

    Science.gov (United States)

    Zhang, Honghua; Liu, Dilong; Hang, Lifeng; Li, Xinyang; Liu, Guangqiang; Cai, Weiping; Li, Yue

    2016-09-30

    A facile route has been proposed for the fabrication of morphology-controlled periodic SiO2 hierarchical micro/nanostructured arrays by reactive ion etching (RIE) using monolayer colloidal crystals as masks. By effectively controlling the experimental conditions of RIE, the morphology of a periodic SiO2 hierarchical micro/nanostructured array could be tuned from a dome-shaped one to a circular truncated cone, and finally to a circular cone. After coating a silver thin layer, these periodic micro/nanostructured arrays were used as surface-enhanced Raman scattering (SERS)-active substrates and demonstrated obvious SERS signals of 4-Aminothiophenol (4-ATP). In addition, the circular cone arrays displayed better SERS enhancement than those of the dome-shaped and circular truncated cone arrays due to the rougher surface caused by physical bombardment. After optimization of the circular cone arrays with different periodicities, an array with the periodicity of 350 nm exhibits much stronger SERS enhancement and possesses a low detection limit of 10(-10) M 4-ATP. This offers a practical platform to conveniently prepare SERS-active substrates.

  12. Large area multi-channel plasmonic absorber based on the touching triangular dimers fabricated by angle controlled colloidal nanolithography

    Science.gov (United States)

    Hamidi, S. M.; Behjati, S.

    2018-02-01

    Here we introduce large area plasmonic touching triangular dimers by angle controlled colloidal nanolithography to use them as an efficient multi channel absorber and also high figure of merit sensors. For this purpose, we coated gold thin films onto nanometric and also micrometric polystyrene hexagonal closed packed masks in different deposition angles and also diverse substrate polar angles. Our prepared samples, after remove masks, show large area touching triangular pattern with different inter particle distances in greater polar angles. To get more sense about optical response of the samples such as transmittance and also electric field distribution, we use finite difference time domain method in simulation part. The transmittance plot shows one narrow or multi-channel adjustable deep depend on inter-particle distances which can be controlled by azimuthally angle in nano lithography process. Also, due to the isoelliptical points in the transmittance spectra; we can see the bright and dark plasmon modes coupling and thus the Fano like resonance takes place in the optical spectral region which is very useful for refractive index measurement.

  13. Anomalous Fluorescence Enhancement from Double Heterostructure 3D Colloidal Photonic Crystals–A Multifunctional Fluorescence-Based Sensor Platform

    Science.gov (United States)

    Eftekhari, Ehsan; Li, Xiang; Kim, Tak H.; Gan, Zongsong; Cole, Ivan S.; Zhao, Dongyuan; Kielpinski, Dave; Gu, Min; Li, Qin

    2015-01-01

    Augmenting fluorescence intensity is of vital importance to the development of chemical and biochemical sensing, imaging and miniature light sources. Here we report an unprecedented fluorescence enhancement with a novel architecture of multilayer three-dimensional colloidal photonic crystals self-assembled from polystyrene spheres. The new technique uses a double heterostructure, which comprises a top and a bottom layer with a periodicity overlapping the excitation wavelength (E) of the emitters, and a middle layer with a periodicity matching the fluorescence wavelength (F) and a thickness that supports constructive interference for the excitation wavelength. This E-F-E double heterostructure displays direction-dependent light trapping for both excitation and fluorescence, coupling the modes of photonic crystal with multiple-beam interference. The E-F-E double heterostructure renders an additional 5-fold enhancement to the extraordinary FL amplification of Rhodamine B in monolithic E CPhCs, and 4.3-fold acceleration of emission dynamics. Such a self-assembled double heterostructue CPhCs may find significant applications in illumination, laser, chemical/biochemical sensing, and solar energy harvesting. We further demonstrate the multi-functionality of the E-F-E double heterostructure CPhCs in Hg (II) sensing. PMID:26400503

  14. Anomalous Fluorescence Enhancement from Double Heterostructure 3D Colloidal Photonic Crystals--A Multifunctional Fluorescence-Based Sensor Platform.

    Science.gov (United States)

    Eftekhari, Ehsan; Li, Xiang; Kim, Tak H; Gan, Zongsong; Cole, Ivan S; Zhao, Dongyuan; Kielpinski, Dave; Gu, Min; Li, Qin

    2015-09-24

    Augmenting fluorescence intensity is of vital importance to the development of chemical and biochemical sensing, imaging and miniature light sources. Here we report an unprecedented fluorescence enhancement with a novel architecture of multilayer three-dimensional colloidal photonic crystals self-assembled from polystyrene spheres. The new technique uses a double heterostructure, which comprises a top and a bottom layer with a periodicity overlapping the excitation wavelength (E) of the emitters, and a middle layer with a periodicity matching the fluorescence wavelength (F) and a thickness that supports constructive interference for the excitation wavelength. This E-F-E double heterostructure displays direction-dependent light trapping for both excitation and fluorescence, coupling the modes of photonic crystal with multiple-beam interference. The E-F-E double heterostructure renders an additional 5-fold enhancement to the extraordinary FL amplification of Rhodamine B in monolithic E CPhCs, and 4.3-fold acceleration of emission dynamics. Such a self-assembled double heterostructure CPhCs may find significant applications in illumination, laser, chemical/biochemical sensing, and solar energy harvesting. We further demonstrate the multi-functionality of the E-F-E double heterostructure CPhCs in Hg (II) sensing.

  15. Human hemoglobin adsorption onto colloidal cerium oxide nanoparticles: a new model based on zeta potential and spectroscopy measurements.

    Science.gov (United States)

    Mobasherat Jajroud, Sheida Yousefi; Falahati, Mojtaba; Attar, Farnoosh; Khavari-Nejad, Ramazan Ali

    2017-09-18

    The nanoparticle (NP)-induced conformational changes of protein and NP agglomeration have gained a remarkable interest in medical and biotechnological fields. Herein, the effect of human hemoglobin (Hb) on the colloidal stability of cerium oxide NP (CNP) was investigated by dynamic light scattering (DLS), zeta potential, and TEM analysis. In addition, the effect of CNP on the heme degradation and structural changes of Hb was studied using fluorescence, circular dichroism (CD), and UV-visible (UV-vis) spectroscopic methods. DLS and TEM analysis showed that the presence of Hb can increase the mean diameter of CNP. Zeta potential measurements revealed that CNP demonstrated a higher charge distribution relative to CNP/Hb complex. Besides, fluorescence studies indicated that two fluorescent heme degradation products are revealed during the interaction of CNP with Hb. Near UV-CD spectroscopy also showed that the microenvironmental changes of heme groups occur after interaction of Hb with CNP. The result of thermal behavior of Hb confirmed the structural changes of protein, which referred to decrease in the Hb stability in the presence of CNP. Indeed, the finding related to structural and functional changes of Hb induced by CNP may be crucial to obtain information regarding the side effects of NPs. Finally, this data reveal much insight into the effects of the interaction on protein structural changes and NP agglomeration, and can correlate the zeta potential of NP-protein complexes with the nature of the principle NP-protein interaction.

  16. Molecular Recognition in the Colloidal World.

    Science.gov (United States)

    Elacqua, Elizabeth; Zheng, Xiaolong; Shillingford, Cicely; Liu, Mingzhu; Weck, Marcus

    2017-11-21

    Colloidal self-assembly is a bottom-up technique to fabricate functional nanomaterials, with paramount interest stemming from programmable assembly of smaller building blocks into dynamic crystalline domains and photonic materials. Multiple established colloidal platforms feature diverse shapes and bonding interactions, while achieving specific orientations along with short- and long-range order. A major impediment to their universal use as building blocks for predesigned architectures is the inability to precisely dictate and control particle functionalization and concomitant reversible self-assembly. Progress in colloidal self-assembly necessitates the development of strategies that endow bonding specificity and directionality within assemblies. Methodologies that emulate molecular and polymeric three-dimensional (3D) architectures feature elements of covalent bonding, while high-fidelity molecular recognition events have been installed to realize responsive reconfigurable assemblies. The emergence of anisotropic 'colloidal molecules', coupled with the ability to site-specifically decorate particle surfaces with supramolecular recognition motifs, has facilitated the formation of superstructures via directional interactions and shape recognition. In this Account, we describe supramolecular assembly routes to drive colloidal particles into precisely assembled architectures or crystalline lattices via directional noncovalent molecular interactions. The design principles are based upon the fabrication of colloidal particles bearing surface-exposed functional groups that can undergo programmable conjugation to install recognition motifs with high fidelity. Modular and versatile by design, our strategy allows for the introduction and integration of molecular recognition principles into the colloidal world. We define noncovalent molecular interactions as site-specific forces that are predictable (i.e., feature selective and controllable complementary bonding partners

  17. Conductivity modeling of gas sensors based on copper ...

    African Journals Online (AJOL)

    On the lower side of the substrate, a screen-printed platinum resistor is devoted to sensor temperature control (Fig. 1). Interdigitated Pt electrodes (IDEs), polarized under 1 volt dc, are used to measure conductivity variations of the CuPc thin film which depend, in time, of gas concentration in sensor environment [26].

  18. On conduction mechanism in paramagnetic phase of Gd based ...

    Indian Academy of Sciences (India)

    hole doping (x) and random disorder of the A site. It has been known for decades that the magnetic phases and elec- tronic properties of these manganites vary .... If the thermal energy is sufficient to overcome the bandgap the electron becomes free to conduct. The expres- sion for resistivity can be written in the following ...

  19. Ionic conductivity and diffusion coefficient of barium-chloride-based ...

    Indian Academy of Sciences (India)

    2017-07-26

    Jul 26, 2017 ... Therefore this polymer electrolyte can be further studied for the development of electrochemical device applications. Keywords. Polymer electrolytes; impedance spectroscopy; diffusion coefficient; ionic conductivity. 1. Introduction .... The structural characterization of BaCl2-doped polymer elec- trolytes was ...

  20. A regularized, model-based approach to phase-based conductivity mapping using MRI.

    Science.gov (United States)

    Ropella, Kathleen M; Noll, Douglas C

    2017-11-01

    To develop a novel regularized, model-based approach to phase-based conductivity mapping that uses structural information to improve the accuracy of conductivity maps. The inverse of the three-dimensional Laplacian operator is used to model the relationship between measured phase maps and the object conductivity in a penalized weighted least-squares optimization problem. Spatial masks based on structural information are incorporated into the problem to preserve data near boundaries. The proposed Inverse Laplacian method was compared against a restricted Gaussian filter in simulation, phantom, and human experiments. The Inverse Laplacian method resulted in lower reconstruction bias and error due to noise in simulations than the Gaussian filter. The Inverse Laplacian method also produced conductivity maps closer to the measured values in a phantom and with reduced noise in the human brain, as compared to the Gaussian filter. The Inverse Laplacian method calculates conductivity maps with less noise and more accurate values near boundaries. Improving the accuracy of conductivity maps is integral for advancing the applications of conductivity mapping. Magn Reson Med 78:2011-2021, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  1. Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene

    KAUST Repository

    Mansour, Ahmed E.

    2016-11-25

    The continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However

  2. Highly anisotropic electric conductivity in PAN-based carbon nanofibers

    Science.gov (United States)

    Aprojanz, J.; Dreyer, B.; Wehr, M.; Wiegand, J.; Baringhaus, J.; Koch, J.; Renz, F.; Sindelar, R.; Tegenkamp, C.

    2017-12-01

    In addition to the chemical and physical properties of nanostructures their successful utilization for applications is strongly triggered by economic aspects. Electrospinning of nanowires from solution followed by subsequent annealing steps is a comparably cheap technique to fabricate conductive carbon nanofibers (CNF) made from polyacrylonitrile (PAN) molecules in large quantities. In this work, we investigated the microscopic properties of the CNFs with diameters of 100-300 nm by means of Raman and x-ray photoelectron spectroscopy and correlated these results with transport measurements done with a 4-tip STM. In particular, we investigated the effect of fiber alignment and knot densities, which can be controlled by applying constant creep due to stress during the stabilization process. The comparison of the conductivity obtained from single CNFs revealed further that the fiber crossings within the ensemble structure act as scattering centers and proofs that the transport is along the surfaces of the CNFs.

  3. Silver nanowire-based transparent, flexible, and conductive thin film

    Directory of Open Access Journals (Sweden)

    Liu Cai-Hong

    2011-01-01

    Full Text Available Abstract The fabrication of transparent, conductive, and uniform silver nanowire films using the scalable rod-coating technique is described in this study. Properties of the transparent conductive thin films are investigated, as well as the approaches to improve the performance of transparent silver nanowire electrodes. It is found that silver nanowires are oxidized during the coating process. Incubation in hydrogen chloride (HCl vapor can eliminate oxidized surface, and consequently, reduce largely the resistivity of silver nanowire thin films. After HCl treatment, 175 Ω/sq and approximately 75% transmittance are achieved. The sheet resistivity drops remarkably with the rise of the film thickness or with the decrease of transparency. The thin film electrodes also demonstrated excellent flexible stability, showing < 2% resistance change after over 100 bending cycles.

  4. Proton-conducting polymer electrolytes based on methacrylates

    Czech Academy of Sciences Publication Activity Database

    Reiter, Jakub; Velická, Jana; Míka, M.

    2008-01-01

    Roč. 53, č. 26 (2008), s. 7769-7774 ISSN 0013-4686 R&D Projects: GA ČR GA106/04/1279; GA AV ČR KJB400320701; GA MŠk LC523; GA ČR(CZ) GA104/06/1471 Institutional research plan: CEZ:AV0Z40320502 Keywords : polymer electrolyte * proton conductivity * phosporic acid Subject RIV: CA - Inorganic Chemistry Impact factor: 3.078, year: 2008

  5. Ionic conductivity studies of gel polyelectrolyte based on ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Cha, E.H. [The Faculty of Liberal Arts (Chemistry), Hoseo University, Asan Choongnam 336-795 (Korea); Lim, S.A. [Functional Proteomics Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea); Park, J.H. [Department of Herbal Medicine, Hoseo University, Asan Choongnam 336-795 (Korea); Kim, D.W. [Department of Chemical Technology, Han Bat National University, Daejon 305-719 (Korea); Macfarlane, D.R. [School of Chemistry, Monash University, Clayton, Vic. 3800 (Australia)

    2008-04-01

    Novel lithium polyelectrolyte-ionic liquids have been prepared and characterized of their properties. Poly(lithium 2-acrylamido-2-methyl propanesulfonate) (PAMPSLi) and its copolymer with N-vinyl formamide (VF) also has been prepared as a copolymer. 1-Ethyl-3-methylimidazolium tricyanomethanide (emImTCM) and N,N-dimethyl-N-propyl-N-butyl ammonium tricyanomethanide (N{sub 1134}TCM) which are chosen because of the same with the anion of ionic liquid were prepared. The ionic conductivity of copolymer system (PAMPSLi/PVF/emImTCM: 5.43 x 10{sup -3} S cm{sup -1} at 25 C) exhibits about over four times higher than that of homopolymer system (PAMPSLi/emImTCM: 1.28 x 10{sup -3} S cm{sup -1} at 25 C). Introduction of vinyl formamide into the copolymer type can increase the dissociation of the lithium cations from the polymer backbone. The ionic conductivity of copolymer with emImTCM (PAMPSLi/PVF/emImTCM) exhibits the higher conductivity than that of PAMPSLi/PVF/N{sub 1134}TCM (2.48 x 10{sup -3} S cm{sup -1}). Because of using the polymerizable anion it is seen to maintain high flexibility of imidazolium cation effectively to exhibit the higher conductivity. And also the viscosity of emImTCM (19.56 cP) is lower than that of N{sub 1134}TCM (28.61 cP). Low viscosity leads to a fast rate of diffusion of redox species. (author)

  6. Laboratory observations and mathematical modeling of colloid-facilitated contaminant transport in chemically heterogeneous systems

    Science.gov (United States)

    Saiers, James E.

    2002-04-01

    In the work reported here, I examine colloid-facilitated solute transport through a natural porous medium that exhibits grain-scale heterogeneity in chemical composition. I conducted six column experiments using the contaminant hydroxyatrazine (HA) and either homogeneous clay-colloid suspensions or mixtures of clay colloids and dissolved organic matter. The transport of colloids composed of illite and montmorillonite, although not conservative, is only slightly affected by rate-limited mass transfer reactions with the oxide-coated aquifer material. Coinjection of HA with monomineralogic suspensions of illite colloids produces modest increases in effluent concentrations of HA relative to experiments performed with colloid-free influent solutions. Montmorillonite colloids have a much higher capacity to bind HA than illite colloids and substantially increase the transport rate of HA in the column experiments. Suwannee River humic acid (SRHA) does not strongly complex aqueous phase HA, but its addition to column influent mixtures that contain HA and montmorillonite suppresses HA adsorption to the clay colloids and promotes a decline in HA mobility. A model for colloid-facilitated transport, formulated to account for nonuniformity in the kinetics of colloid deposition and HA adsorption, closely describes HA transport in experiments performed with monomineralogic clay-colloid suspensions, heterogeneous suspensions made of both illite and montmorillonite, and mixtures of montmorillonite and SRHA.

  7. Training Teachers to Conduct Trial-Based Functional Analyses

    Science.gov (United States)

    Kunnavatana, S. Shanun; Bloom, Sarah E.; Samaha, Andrew L.; Dayton, Elizabeth

    2013-01-01

    The trial-based functional analysis (FA) is a promising approach to identification of behavioral function and is especially suited for use in educational settings. Not all studies on trial-based FA have included teachers as therapists, and those studies that have, included minimal information on teacher training. The purpose of this study was to…

  8. Structural color from colloidal glasses

    Science.gov (United States)

    Magkiriadou, Sofia

    When a material has inhomogeneities at a lengthscale comparable to the wavelength of light, interference can give rise to structural colors: colors that originate from the interaction of the material's microstructure with light and do not require absorbing dyes. In this thesis we study a class of these materials, called photonic glasses, where the inhomogeneities form a dense and random arrangement. Photonic glasses have angle-independent structural colors that look like those of conventional dyes. However, when this work started, there was only a handful of colors accessible with photonic glasses, mostly hues of blue. We use various types of colloidal particles to make photonic glasses, and we study, both theoretically and experimentally, how the optical properties of these glasses relate to their structure and constituent particles. Based on our observations from glasses of conventional particles, we construct a theoretical model that explains the scarcity of yellow, orange, and red photonic glasses. Guided by this model, we develop novel colloidal systems that allow a higher degree of control over structural color. We assemble glasses of soft, core-shell particles with scattering cores and transparent shells, where the resonant wavelength can be tuned independently of the reflectivity. We then encapsulate glasses of these core-shell particles into emulsion droplets of tunable size; in this system, we observe, for the first time, angle-independent structural colors that cover the entire visible spectrum. To enhance color saturation, we begin experimenting with inverse glasses, where the refractive index of the particles is lower than the refractive index of the medium, with promising results. Finally, based on our theoretical model for scattering from colloidal glasses, we begin an exploration of the color gamut that could be achieved with this technique, and we find that photonic glasses are a promising approach to a new type of long-lasting, non-toxic, and

  9. Saturated Zone Colloid-Facilitated Transport

    International Nuclear Information System (INIS)

    Wolfsberg, A.; Reimus, P.

    2001-01-01

    and interpretation from the C-wells reactive tracer testing complex in the saturated zone of Yucca Mountain. As no data regarding colloid transport have been developed by the Yucca Mountain Site Characterization Project (YMP) for the alluvial system, a theoretical analysis based on studies performed in other alluvial systems is developed. The parameters derived in this AMR are developed in a manner consistent with the PA methodology and can be readily integrated into that analysis

  10. Thermography Used to Test Conductivity of Carbon Based Cloth

    Science.gov (United States)

    Craven, Paul

    2012-01-01

    Testing of the ability of carbon fiber to radiatively cool a heat source. The carbon fibers are attached to a heat source. The heat conducts into the fiber than along the fiber away from the heat source. The test are done in a vacuum chamber (10-5 Torr typical). The IR camera is viewing the fiber through a ZnSe window. A thermocouple (TC) in contact with the fiber is at the top right hand side of the area of interest and one is near the bottom. Thin shielding fins, seen edge on, are just above the top thermocouple.

  11. Medical applications of colloids

    CERN Document Server

    Matijevic, Egon

    2008-01-01

    The first book of its type on the medical and biomedical applications of colloids, although there are some related titles on different topicsDiscusses the effects of uniform particles in drug formulations and releaseEvaluates particle transport and deposition in the human body.

  12. Binary colloidal crystals

    NARCIS (Netherlands)

    Christova-Zdravkova, C.G.

    2005-01-01

    Binary crystals are crystals composed of two types of particles having different properties like size, mass density, charge etc. In this thesis several new approaches to make binary crystals of colloidal particles that differ in size, material and charge are reported We found a variety of crystal

  13. Enhanced thermal conductivity of nano-SiC dispersed water based ...

    Indian Academy of Sciences (India)

    lored quasi-single phase medium comprising stable colloidal dispersion of ultra fine or nanometric (< 100 nm) .... a uniform and stable suspension (like a colloid), and pre- clude agglomeration or chemical change of ..... primarily responsible for phonon or heat transport from par- ticle to particle within the fluid than the atoms ...

  14. Self-assembly of colloidal surfactants

    Science.gov (United States)

    Kegel, Willem

    2012-02-01

    We developed colloidal dumbbells with a rough and a smooth part, based on a method reported in Ref. [1]. Specific attraction between the smooth parts occurs upon addition of non-adsorbing polymers of appropriate size. We present the first results in terms of the assemblies that emerge in these systems. [4pt] [1] D.J. Kraft, W.S. Vlug, C.M. van Kats, A. van Blaaderen, A. Imhof and W.K. Kegel, Self-assembly of colloids with liquid protrusions, J. Am. Chem. Soc. 131, 1182, (2009)

  15. Reversibility of sorption of plutonium-239 onto hematite and goethite colloids

    International Nuclear Information System (INIS)

    Lu, N.; Cotter, C.R.; Kitten, H.D.; Bentley, J.; Triay, I.R.

    1998-01-01

    Laboratory batch sorption experiments were conducted to evaluate: (1) sorption of plutonium-239 ( 239 Pu) on different iron oxide colloids (hematite and geothite), (2) sorption kinetics of colloidal Pu(IV) and soluble Pu(V) onto these two colloids, and (3) desorption of colloidal Pu(IV) and soluble Pu(V) from 239 Pu-loaded colloids as a function of time. Natural groundwater and carbonate-rich synthetic groundwater were used in this study. To examine the possible influence of bicarbonate on 239 Pu sorption, an additional set of experiments was conducted in sodium nitrate (NaNO 3 ) solutions under carbon dioxide free environments. Our results show that colloidal Pu(IV) as well as soluble Pu(V) was rapidly adsorbed by hematite and goethite colloids in both natural and synthetic groundwater. The amount of 239 Pu adsorbed by both iron oxide colloids in synthetic groundwater was higher than in natural groundwater. The presence of carbonate did not influence the sorption of 239 Pu. While sorption of soluble Pu(V) is a slow process, sorption of colloidal Pu(IV) occurs rapidly. Desorption of Pu from iron oxide colloids is much slower than the sorption processes. Our findings suggest that different sorption and desorption behaviors of 239 Pu by iron oxide colloids in groundwater may facilitate the transport of 239 Pu along potential flowpaths from the areas contaminated by radionuclide and release to the accessible environment. (orig.)

  16. Dense ceramic membranes based on ion conducting oxides

    International Nuclear Information System (INIS)

    Fontaine, M.L.; Larring, Y.; Bredesen, R.; Norby, T.; Grande, T.

    2007-01-01

    This chapter reviews the recent progress made in the fields of high temperature oxygen and hydrogen separation membranes. Studies of membranes for oxygen separation are mainly focusing on materials design to improve flux, and to lesser extent, related to stability issues. High oxygen fluxes satisfying industrial requirements can be obtained but, for many materials, the surface exchange rate is limiting the performance. The current status on electrolyte-type and mixed proton and electron conducting membranes is outlined, highlighting materials with improved stability in typical applications as solid oxide fuel cell technology and gas separation. In our presentation more fundamental aspects related to transport properties, chemical and mechanical stability of membrane materials are also treated. It is concluded that a significantly better understanding of the long term effects of operation in chemical gradients is needed for these types of membrane materials. (authors)

  17. An innovative ionization chamber based on conducting polymer electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Luiz Antonio P. [Centro Regional de Ciencias Nucleares (CRCN), Recife, PE (Brazil)]. E-mail: lasantos@cnen.gov.br; Araujo, Elmo S.; Amazonas, Irami B. [Pernambuco Univ., Recife, PE (Brazil). Dept. de Energia Nuclear]. E-mail: esa@ufpe.br; Azevedo, Walter M. [Pernambuco Univ., Recife, PE (Brazil). Dept. de Quimica Fundamental]. E-mail: wma@ufpe.br

    2005-07-01

    A parallel-plate ionization chamber was developed to be used as detector for X-ray radiation measurements. The innovation here is the fact that there are no graphite or metallic electrodes as usually, but the proposed radiation detector was built with polyaniline (PANI) conducting polymer instead. A PANI thin film was chemically deposited on the surface of poly(methyl methacrylate) (PMMA) substrate. The PMMA layer can minimize the radiation beam attenuation effects and make the detector more robust. An HF-160 PANTAK unit was used to generate X-ray beam from 40 kV to 140 kV potentials. A Flip-flop electrometer was used as current read-out system. The results from proposed ionization chamber were compared with a PTW2532 standard ionization chamber. Preliminary results such as energy dependence and saturation curves have already been presented recently and here is presented additional results: angular dependence and some results concerning repeatability of the device under working circumstance and its response when the dose rate is changed. The results strongly indicate that the developed ion chamber can be used in diagnostic X-ray range for dosimetry applications. (author)

  18. Liquid electrolytes based on new lithium conductive imidazole salts

    Energy Technology Data Exchange (ETDEWEB)

    Niedzicki, L.; Kasprzyk, M.; Kuziak, K.; Zukowska, G.Z.; Marcinek, M.; Wieczorek, W. [Department of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw (Poland); Armand, M. [LRCS, University de Picardie Jules Verne, UMR 6007 CNRS, 33 rue de Saint-Leu, 80039 Amiens (France)

    2011-02-01

    In the present paper new generation of imidazole-derived lithium salts (LiTDI - lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide, LiPDI - lithium 4,5-dicyano-2-(pentafluoroethyl)imidazolide and LiHDI - lithium 4,5-dicyano-2-(n-heptafluoropropyl)imidazolide) applied in a model liquid electrolyte, with propylene carbonate used as a solvent, is described. Room temperature ionic conductivities measured by Impedance Spectroscopy are as high as 10{sup -2} to 10{sup -3} S cm{sup -1} for the 0.1-1 mol dm{sup -3} salt concentration range. Lithium cation transference numbers calculated using the Bruce-Vincent method exceed 0.4 at salt concentration equal to 1 mol dm{sup -3}. Interface resistance measurements showed good stability at high - 0.5 mol dm{sup -3} or low - 0.01 mol dm{sup -3} salt concentrations. Ionic associations were estimated using Fuoss-Kraus semiempirical method revealing relatively low association rates. The effect of anion structure on ionic interactions and electrochemical characteristics of the studied electrolytes is discussed. (author)

  19. Colloidal silica-grouting in demonstration tunnel 2 in ONKALO

    International Nuclear Information System (INIS)

    Hollmen, K.; Sievaenen, U.; Funehag, J.; Granberg, N.; Lyytinen, T.; Syrjaenen, P.

    2013-12-01

    Posiva carried out grouting using colloidal silica as the grouting material and with the time stop method as the design approach.Three fans were pre-grouted at Posiva Oy's research space ONKALO demonstration tunnel 2 in autumn 2011 and early winter 2012. Colloidal silica is a mix of one-component colloidal silica and accelerator. Before gelling, colloidal silica behaves like a Newtonian liquid. Colloidal silica's efficiency of penetrating hydraulic apertures in small fractures in rock is significantly better than that of cement-based grout. The grouting design was based on an analytical calculation model. A new technique was used in the grouting implementation, which primarily differed from the previous technique in regard to vacuum pumping and packers. The goal of the first grouting fan in the demonstration tunnel was to check the functionality of the equipment and the method; therefore, the fan was drilled into rock mass with no hydraulic conducting fractures. The second grouting fan was drilled into rock mass with an observed fairly low hydraulic conductivity that was lower than the start criterion established in Posiva Oy's requirements to manage groundwater inflows. Nevertheless, the grouting was carried out. The sealing effect was estimated from the control holes, and a slight improvement in sealing was noted. The holes of the third grouting fan clearly penetrated a water conductive rock mass. The grouting was carried out in two phases, in which the new holes in the second phase were drilled between the existing ones that were drilled in the first phase. In the third fan, the grouting holes of the first phase were noted to be significantly crooked and the second phase grouting holes were drilled in locations that differed from the original design. The quantity of grouting holes was increased in the second phase. The sealing effect was estimated by monitoring the second phase holes and control holes. Based on observations from the control holes

  20. Enhanced transport of ferrihydrite colloid by chain-shaped humic acid colloid in saturated porous media.

    Science.gov (United States)

    Ma, Jie; Guo, Huaming; Lei, Mei; Li, Yongtao; Weng, Liping; Chen, Yali; Ma, Yuling; Deng, Yingxuan; Feng, Xiaojuan; Xiu, Wei

    2018-04-15

    Both humic acid and colloid particle size effectively regulate colloid transport. However, little is known about effect of particle size and configuration of humic acid colloid (HA colloid ) on enhanced-transport of ferrihydrite colloid (FH colloid ) in porous media. Co-transport of HA colloid and FH colloid at different pH was systematically investigated by monitoring breakthrough curves (BTCs) in saturated sand columns. The colloid transport model and the (X)DLVO theory were used to reveal the mechanism of HA colloid -enhanced FH colloid transport in the columns. Results showed that HA colloid enhanced FH colloid transport in neutral and alkaline conditions. In neutral conditions, small HA colloid (F-HA colloid ) with chain-shaped structure enhanced FH colloid transport more prominently than pristine granular HA colloid . The chain-shaped F-HA colloid caused osmotic repulsion and elastic-steric repulsion between colloids and sand, leading to enhanced transport. However, the granular HA colloid readily occurred as deposition due to attachment and straining, which decreased the enhanced transport of FH colloid . In alkaline conditions, both HA colloid and F-HA colloid were chain-shaped, with longer chains of HA colloid than F-HA colloid . Ferrihydrite colloid transport was enhanced by HA colloid more significantly than F-HA colloid due to stronger repulsion between mixed HA colloid -FH colloid and sand. It suggested that regulation of particle size and morphology of HA colloid would enhance FH colloid transport and further help in understanding FH colloid -facilitated contaminants transport in porous media. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Transport and Deposition of Variably Charged Soil Colloids in Saturated Porous Media

    DEFF Research Database (Denmark)

    Sharma, Anu; Kawmoto, Ken; Møldrup, Per

    2012-01-01

    A series of column experiments was conducted to investigate the transport and deposition of variably charged colloids in saturated porous media. Soil colloids with diameters ... Okinawa (RYS colloids) in Japan. The VAS colloids exhibited a negative surface charge with a high pH dependency, whereas the RYS colloids exhibited a negative surface charge with less pH dependency. The soil colloids were applied as colloidal suspensions to 10-cm-long saturated sand columns packed...... with either Narita sand (mean diameter = 0.64 mm) or Toyoura sand (mean diameter = 0.21 mm) at different flow rates, suspension concentrations, and pH conditions. Both sands exhibited a negative surface charge in the measured pH range, but the pH dependency was more pronounced for the Toyoura sand...

  2. Colloid straining within saturated heterogeneous porous media.

    Science.gov (United States)

    Porubcan, Alexis A; Xu, Shangping

    2011-02-01

    The transport of 0.46 μm, 2.94 μm, 5.1 μm and 6.06 μm latex particles in heterogeneous porous media prepared from the mixing of 0.78 mm, 0.46 mm and 0.23 mm quartz sands was investigated through column transport experiments. It was observed that the 0.46 μm particles traveled conservatively within the heterogeneous porous media, suggesting that under the experimental conditions employed in this research the strong repulsive interactions between the negatively charged latex particles and the clean quartz sands led to minimal colloid immobilization due to physicochemical filtration. The immobilization of the 2.94 μm, 5.1 μm and 6.06 μm latex particles was thus attributed to colloid straining. Experimental results showed that the straining of colloidal particles within heterogeneous sand mixtures increased when the fraction of finer sands increased. The mathematical model that was developed and tested based on results obtained using uniform sands (Xu et al., 2006) was found to be able to describe colloid straining within heterogeneous porous media. Examination of the relationship between the best-fit values of the clean-bed straining rate coefficients (k(0)) and the ratio of colloid diameter (d(p)) and sand grain size (d(g)) indicated that when number-average sizes were used to represent the size of the heterogeneous porous media, there existed a consistent relationship for both uniform sands and heterogeneous sand mixtures. Similarly, the use of the number-averaged sizes for the heterogeneous porous media produced a uniform relationship between the colloid straining capacity term (λ) and the ratio of d(p)/d(g) for all the sand treatments. © 2010 Elsevier Ltd. All rights reserved.

  3. Investigation of ITO free transparent conducting polymer based electrode

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Vikas; Sapna,; Sachdev, Kanupriya [Department of Physics, Malaviya National Institute of Technology Jaipur, JLN Marg, Jaipur-India-302017 (India)

    2016-05-23

    The last few decades have seen a significant improvement in organic semiconductor technology related to solar cell, light emitting diode and display panels. The material and structure of the transparent electrode is one of the major concerns for superior performance of devices such as OPV, OLED, touch screen and LCD display. Commonly used ITO is now restricted due to scarcity of indium, its poor mechanical properties and rigidity, and mismatch of energy levels with the active layer. Nowadays DMD (dielectric-metal-dielectric) structure is one of the prominent candidates as alternatives to ITO based electrode. We have used solution based spin coated polymer layer as the dielectric layer with silver thin film embedded in between to make a polymer-metal-polymer (PMP) structure for TCE applications. The PMP structure shows low resistivity (2.3 x 10{sup −4}Ω-cm), high carrier concentration (2.9 x 10{sup 21} cm{sup −3}) and moderate transparency. The multilayer PMP structure is characterized with XRD, AFM and Hall measurement to prove its suitability for opto-electronic device applications.

  4. Concepts and techniques for conducting performance-based audits

    International Nuclear Information System (INIS)

    Espy, I.J.

    1990-01-01

    Quality assurance (QA) audits have historically varied in purpose and approach and have earned labels that attempt to name each type of audit. Some more common labels for QA audits include compliance, program, product, and performance-based. While documentation and methodologies are important and hence controlled, an organizations product has ultimate impact on the user. Product quality then must be of more concern to the user than documentation and methodologies of the provider. Performance-based auditing (PBA) provides for assessing product quality by evaluating the suppliers activities that produce and affect product quality. PBA is defined as auditing that evaluates the ability of an activity to regularly produce and release only acceptable product, where product refers to the output of the activity. The output may be hardware, software, or a service, and acceptability includes suitability to the users needs. To satisfy this definition, PBA should focus on the activities that produce and affect product and should evaluate the systematics of each activity in terms of its ability to produce acceptable product. The activity evaluation model provides a framework for evaluating the systematicness of any activity. Elements of the activity evaluation model are described

  5. Characteristics of Natural Colloids in the Saturated Alluvium South of Yucca Mountain, Nevada

    Science.gov (United States)

    Kung, S.; Chipera, S. J.; Reimus, P. W.

    2001-12-01

    conducting radionuclide sorption studies using natural colloids as the sorbing substrate to further assess the potential for colloid-facilitated radionuclide transport in the alluvium.

  6. Conducting Meta-Analyses Based on p Values

    Science.gov (United States)

    van Aert, Robbie C. M.; Wicherts, Jelte M.; van Assen, Marcel A. L. M.

    2016-01-01

    Because of overwhelming evidence of publication bias in psychology, techniques to correct meta-analytic estimates for such bias are greatly needed. The methodology on which the p-uniform and p-curve methods are based has great promise for providing accurate meta-analytic estimates in the presence of publication bias. However, in this article, we show that in some situations, p-curve behaves erratically, whereas p-uniform may yield implausible estimates of negative effect size. Moreover, we show that (and explain why) p-curve and p-uniform result in overestimation of effect size under moderate-to-large heterogeneity and may yield unpredictable bias when researchers employ p-hacking. We offer hands-on recommendations on applying and interpreting results of meta-analyses in general and p-uniform and p-curve in particular. Both methods as well as traditional methods are applied to a meta-analysis on the effect of weight on judgments of importance. We offer guidance for applying p-uniform or p-curve using R and a user-friendly web application for applying p-uniform. PMID:27694466

  7. New collector efficiency equation for colloid filtration in both natural and engineered flow conditions

    Science.gov (United States)

    Nelson, Kirk E.; Ginn, Timothy R.

    2011-05-01

    A new equation for the collector efficiency (η) of the colloid filtration theory (CFT) is developed via nonlinear regression on the numerical data generated by a large number of Lagrangian simulations conducted in Happel's sphere-in-cell porous media model over a wide range of environmentally relevant conditions. The new equation expands the range of CFT's applicability in the natural subsurface primarily by accommodating departures from power law dependence of η on the Peclet and gravity numbers, a necessary but as of yet unavailable feature for applying CFT to large-scale field transport (e.g., of nanoparticles, radionuclides, or genetically modified organisms) under low groundwater velocity conditions. The new equation also departs from prior equations for colloids in the nanoparticle size range at all fluid velocities. These departures are particularly relevant to subsurface colloid and colloid-facilitated transport where low permeabilities and/or hydraulic gradients lead to low groundwater velocities and/or to nanoparticle fate and transport in porous media in general. We also note the importance of consistency in the conceptualization of particle flux through the single collector model on which most η equations are based for the purpose of attaining a mechanistic understanding of the transport and attachment steps of deposition. A lack of sufficient data for small particles and low velocities warrants further experiments to draw more definitive and comprehensive conclusions regarding the most significant discrepancies between the available equations.

  8. Producing colloids with microfluidics

    Science.gov (United States)

    Pannacci, Nicolas; Willaime, Herve; Tabeling, Patrick

    2008-11-01

    Submicronic emulsions are commonly used in pharmaceutical, food, cosmetic and material industries. Standard microfluidic tool is particularly convenient to produce in a very controlled way either droplets of typical diameter ranging from 10 to 300 microns with a perfect monodispersity (nanodrops in a way that is slightly dependent on the fluids used. The control on such a flow authorizes the adjustment of the diameter of the colloids formed. We will show brownian particles from 860 nm to 1.3 μm in diameter obtained in such way and their clustering into crystals thanks to their high monodispersity. These first experimental results are very promising and make evident the great potential of micro and nano-fluidics to produce nano-emulsions or colloids with very controlled size that metamaterials can require.

  9. Fractal nematic colloids

    Science.gov (United States)

    Hashemi, S. M.; Jagodič, U.; Mozaffari, M. R.; Ejtehadi, M. R.; Muševič, I.; Ravnik, M.

    2017-01-01

    Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and numerical modelling. Explicit generation of topological defect pairs is found, with the number of defects following exponential-law dependence and reaching few 100 already at fractal iteration four. This work demonstrates a route for generation of fractal topological defect states in responsive soft matter. PMID:28117325

  10. Parametric Study Conducted of Rocket- Based, Combined-Cycle Nozzles

    Science.gov (United States)

    Steffen, Christopher J., Jr.; Smith, Timothy D.

    1998-01-01

    Having reached the end of the 20th century, our society is quite familiar with the many benefits of recycling and reusing the products of civilization. The high-technology world of aerospace vehicle design is no exception. Because of the many potential economic benefits of reusable launch vehicles, NASA is aggressively pursuing this technology on several fronts. One of the most promising technologies receiving renewed attention is Rocket-Based, Combined-Cycle (RBCC) propulsion. This propulsion method combines many of the efficiencies of high-performance jet aircraft with the power and high-altitude capability of rocket engines. The goal of the present work at the NASA Lewis Research Center is to further understand the complex fluid physics within RBCC engines that govern system performance. This work is being performed in support of NASA's Advanced Reusable Technologies program. A robust RBCC engine design optimization demands further investigation of the subsystem performance of the engine's complex propulsion cycles. The RBCC propulsion system under consideration at Lewis is defined by four modes of operation in a singlestage- to-orbit configuration. In the first mode, the engine functions as a rocket-driven ejector. When the rocket engine is switched off, subsonic combustion (mode 2) is present in the ramjet mode. As the vehicle continues to accelerate, supersonic combustion (mode 3) occurs in the ramjet mode. Finally, as the edge of the atmosphere is approached and the engine inlet is closed off, the rocket is reignited and the final accent to orbit is undertaken in an all-rocket mode (mode 4). The performance of this fourth and final mode is the subject of this present study. Performance is being monitored in terms of the amount of thrust generated from a given amount of propellant.

  11. Influence of Conductive and Semi-Conductive Nanoparticles on the Dielectric Response of Natural Ester-Based Nanofluid Insulation

    Directory of Open Access Journals (Sweden)

    M. Z. H. Makmud

    2018-02-01

    Full Text Available Nowadays, studies of alternative liquid insulation in high voltage apparatus have become increasingly important due to higher concerns regarding safety, sustainable resources and environmentally friendly issues. To fulfil this demand, natural ester has been extensively studied and it can become a potential product to replace mineral oil in power transformers. In addition, the incorporation of nanoparticles has been remarkable in producing improved characteristics of insulating oil. Although much extensive research has been carried out, there is no general agreement on the influence on the dielectric response of base oil due to the addition of different amounts and conductivity types of nanoparticle concentrations. Therefore, in this work, a natural ester-based nanofluid was prepared by a two-step method using iron oxide (Fe2O3 and titanium dioxide (TiO2 as the conductive and semi-conductive nanoparticles, respectively. The concentration amount of each nanoparticle types was varied at 0.01, 0.1 and 1.0 g/L. The nanofluid samples were characterised by visual inspection, morphology and the dynamic light scattering (DLS method before the dielectric response measurement was carried out for frequency-dependent spectroscopy (FDS, current-voltage (I-V, and dielectric breakdown (BD strength. The results show that the dielectric spectra and I-V curves of nanofluid-based iron oxide increases with the increase of iron oxide nanoparticle loading, while for titanium dioxide, it exhibits a decreasing response. The dielectric BD strength is enhanced for both types of nanoparticles at 0.01 g/L concentration. However, the increasing amount of nanoparticles at 0.1 and 1.0 g/L led to a contrary dielectric BD response. Thus, the results indicate that the augmentation of conductive nanoparticles in the suspension can lead to overlapping mechanisms. Consequently, this reduces the BD strength compared to pristine materials during electron injection in high electric

  12. Colloid Facilitated Transport of Plutonium in Fractured Volcanic Tuff

    Science.gov (United States)

    Kersting, A. B.; Zhao, P.; Walensky, J. R.; Roberts, S. K.; Johnson, M. R.; Zavarin, M.; Ramon, E. C.

    2004-12-01

    The transport of low-solubility radionuclides in a colloidal- or colloidal bound state is frequently suspected or observed. Groundwater contaminated with radionuclides associated with underground nuclear tests was collected from several different well locations at the Nevada Test Site (NTS). In each case, the low-levels of plutonium detected in the groundwater were overwhelmingly (>95percent) associated with the colloidal and not the dissolved fraction of the groundwater. The colloidal fractions consisted of secondary minerals such as clays and zeolites. To better understand the mechanisms controlling the potential colloidal transport of plutonium, colloid-facilitated fracture flow laboratory experiments are being conducted. Pseudocolloids consisting of Pu(IV) sorbed to clinoptilolite were combined with a radionuclide solution cocktail consisting of Np, U, Cs, Sr, Sm and 3H and Re (analog to Tc) tracers in NTS-type synthetic groundwater (4.5mM NaHCO3-). The cocktail was injected into a smooth fracture in a volcanic tuff rock core from the NTS and the effluent analyzed. Autoradiography and secondary ion mass spectrometry will be used to understand the mineral -colloid-radionuclide interactions in the fracture volcanic tuff.

  13. Colloid-facilitated transport of cesium in vadose-zone sediments: the importance of flow transients.

    Science.gov (United States)

    Cheng, Tao; Saiers, James E

    2010-10-01

    Colloid-sized particles are commonly detected in vadose-zone pore waters and are capable of binding chemicals with sorptive affinities for geologic materials. Published research demonstrates that colloids are capable of facilitating the transport of sorptive contaminants under conditions of steady pore water flow, when volumetric moisture content and pore water velocity are constant. Less is known about the role of colloids in governing contaminant mobility under transient-flow conditions, which are characteristic of natural vadose-zone environments. The objective of this study is to elucidate the influences of flow transients on the mobilization and transport of in situ colloids and colloid-associated contaminants. We conducted column experiments in which the mobilization of in situ colloids and (137)Cs was induced by transients associated with the drainage and imbibition of (137)Cs contaminated-sediments. Our results demonstrate that substantial quantities of in situ colloids and colloid-associated (137)Cs are mobilized as volumetric moisture content declines during porous-medium drainage and as volumetric moisture content increases during porous-medium imbibition. We also find that the colloid-effect on (137)Cs transport is sensitive to changes in pore water ionic strength. That is, the quantities of colloids mobilized and the capacity of the these colloids to bind (137)Cs decrease with increasing ionic strength, leading to a decrease of the mass of (137)Cs eluted from the columns during porous-medium drainage and imbibition.

  14. Rapid immunofiltration assay based on colloidal gold-protein G conjugate as an alternative screening test for bovine and ovine brucellosis.

    Science.gov (United States)

    Genç, Oktay; Büyüktanır, Ozlem; Yurdusev, Nevzat

    2012-02-01

    A non-enzymatic rapid immunofiltration assay (NERIFA) was developed as an alternative field test for rapid detection of anti-Brucella antibody in bovine and ovine sera. The assay was based on Brucella abortus lipopolysaccharide as diagnostic antigen and colloidal gold particle-protein G conjugate as detection reagent. Its diagnostic performance was evaluated using undiluted well-defined positive and negative serum samples in comparison with Rose Bengal test (RBT), complement fixation test (CFT) and a commercial and an in-house indirect enzyme-linked immunosorbent assay (ELISA). A perfect test agreement was found between NERIFA and ELISAs by kappa statistics. In addition, McNemar's analysis of the results showed that the RBT for bovine sera and the CFT for ovine sera were found significantly less performant than indirect ELISAs and NERIFA. The results of the present study indicated that the NERIFA could be considered as a simple, rapid, and accurate field test for screening of ovine and bovine brucellosis. Therefore, this test constitutes a high potential to be used as an alternative model particularly in brucellosis prevalent tropical and subtropical geographical areas.

  15. Patterned Colloidal Photonic Crystals.

    Science.gov (United States)

    Hou, Jue; Li, Mingzhu; Song, Yanlin

    2018-03-01

    Colloidal photonic crystals (PCs) have been well developed because they are easy to prepare, cost-effective, and versatile with regards to modification and functionalization. Patterned colloidal PCs contribute a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate-induced assembly, inkjet printing, and selective immobilization and modification, is presented. The advantages of patterned PC devices are also discussed in detail, for example, improved detection sensitivity and response speed of the sensors, control over the flow direction and wicking rate of microfluidic channels, recognition of cross-reactive molecules through an array-patterned microchip, fabrication of display devices with tunable patterns, well-arranged RGB units, and wide viewing-angles, and the ability to construct anti-counterfeiting devices with different security strategies. Finally, the perspective of future developments and challenges is presented. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Flocking ferromagnetic colloids.

    Science.gov (United States)

    Kaiser, Andreas; Snezhko, Alexey; Aranson, Igor S

    2017-02-01

    Assemblages of microscopic colloidal particles exhibit fascinating collective motion when energized by electric or magnetic fields. The behaviors range from coherent vortical motion to phase separation and dynamic self-assembly. Although colloidal systems are relatively simple, understanding their collective response, especially under out-of-equilibrium conditions, remains elusive. We report on the emergence of flocking and global rotation in the system of rolling ferromagnetic microparticles energized by a vertical alternating magnetic field. By combing experiments and discrete particle simulations, we have identified primary physical mechanisms, leading to the emergence of large-scale collective motion: spontaneous symmetry breaking of the clockwise/counterclockwise particle rotation, collisional alignment of particle velocities, and random particle reorientations due to shape imperfections. We have also shown that hydrodynamic interactions between the particles do not have a qualitative effect on the collective dynamics. Our findings shed light on the onset of spatial and temporal coherence in a large class of active systems, both synthetic (colloids, swarms of robots, and biopolymers) and living (suspensions of bacteria, cell colonies, and bird flocks).

  17. Towards Practical Application of Paper based Printed Circuits: Capillarity Effectively Enhances Conductivity of the Thermoplastic Electrically Conductive Adhesives

    Science.gov (United States)

    Wu, Haoyi; Chiang, Sum Wai; Lin, Wei; Yang, Cheng; Li, Zhuo; Liu, Jingping; Cui, Xiaoya; Kang, Feiyu; Wong, Ching Ping

    2014-09-01

    Direct printing nanoparticle-based conductive inks onto paper substrates has encountered difficulties e.g. the nanoparticles are prone to penetrate into the pores of the paper and become partially segmented, and the necessary low-temperature-sintering process is harmful to the dimension-stability of paper. Here we prototyped the paper-based circuit substrate in combination with printed thermoplastic electrically conductive adhesives (ECA), which takes the advantage of the capillarity of paper and thus both the conductivity and mechanical robustness of the printed circuitsweredrastically improved without sintering process. For instance, the electrical resistivity of the ECA specimen on a pulp paper (6 × 10-5Ω.cm, with 50 wt% loading of Ag) was only 14% of that on PET film than that on PET film. This improvement has been found directly related to the sizing degree of paper, in agreement with the effective medium approximation simulation results in this work. The thermoplastic nature also enables excellent mechanical strength of the printed ECA to resist repeated folding. Considering the generality of the process and the wide acceptance of ECA technique in the modern electronic packages, this method may find vast applications in e.g. circuit boards, capacitive touch pads, and radio frequency identification antennas, which have been prototyped in the manuscript.

  18. Colloid migration in fractured media

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, J.R. (California Univ., Berkeley, CA (USA). Dept. of Civil Engineering)

    1989-09-15

    Field studies at the Nevada Test Site by researchers at Lawrence Livermore National Laboratory have demonstrated that radionuclides are being transported by colloidal material suspended in groundwater. This observation is counter to most predictions from contaminant transport models because the models assume adsorbed species are immobile. The purpose of this research is to quantify the transport processes for colloidal materials and develop the mechanistic understanding necessary to predict radionuclide transport in fractured media. There were three areas of investigation during this year that have addressed these issues: chemical control of colloid deposition on clean mineral surfaces, colloid accumulation on fracture surfaces, and the influence of deposited colloids on colloid and tracer migration. 7 refs.

  19. Effect of Natural Abiotic Colloids on the Transport of Lindane (gamma-hexachlorocyclohexane) through Saturated Porous Media: Laboratory Experiments and Model-Based Analysis

    Science.gov (United States)

    Ngueleu Kamangou, S.; Cirpka, O. A.; Grathwohl, P.

    2012-04-01

    In many developing countries, the hygienic situation has improved by changing from surface-water bodies to groundwater as drinking water resource. However, failures have frequently been reported, presumably caused by wrong design of groundwater extraction (e.g., wells too close to open-water bodies, landfill leachates or agricultural areas). Moreover threat to groundwater pollution is enhanced when colloidal particles in the subsurface can act as carriers for adsorbing contaminants such as hydrophobic chlorinated organic contaminants. In this study, the main objective was to investigate the influence of particles in the size range of colloids on the subsurface transport of pesticides which are known to cause severe health problems. The model pesticide was gamma-hexachlorocyclohexane, a representative hydrophobic insecticide which is still used mainly in tropical countries. Colloid-facilitated transport was carried out by considering a first case where the adsorption of the contaminant to the particles is at equilibrium before getting simultaneously transported, and a second case where this equilibrium was not reached before their transport. Another focus besides colloid-facilitated transport was placed on the release of the contaminant from trapped colloids. Data analysis was done with the help of numerical modeling and the minimum model complexity needed to simulate such transports was examined.

  20. Ionic strength reduction and flow interruption enhanced colloid-facilitated Hg transport in contaminated soils.

    Science.gov (United States)

    Zhu, Yingjia; Ma, Lena Q; Dong, Xiaoling; Harris, Willie G; Bonzongo, J C; Han, Fengxiang

    2014-01-15

    The effects of ionic strength (IS) reduction (5-0.05mM) and flow interruption (FI, flow stopped for 7d) on colloid and Hg release in the leachate were examined in column experiment. Two Hg contaminated soils (13.9 and 146mg/kg) were used, with Hg concentrations in colloids being 2-4 times greater than bulk soils. Based on sequential extraction, Hg concentrations in organic matter (OM) fraction were the most abundant in soils (31-48%). Column leaching after IS reduction and FI released large amounts of colloidal Hg, accounting for 44-48% of released Hg. The highest colloidal Hg concentrations at 27.8 and 360μg/L were observed at ∼1 pore volume after FI. Concentration distribution of colloidal OM and colloidal Fe was similar to colloidal Hg in the leachate, showing peak concentrations after IS reduction and FI. Most of the released colloidal Hg was in OM fraction (37-53%), with some in Fe/Mn oxide fraction (11-19%). Based on composition of released colloids and Hg fractionation in soils and colloids, colloidal OM could serve as an important carrier for Hg transport in soils. Published by Elsevier B.V.

  1. A novel two-dimensional model for colloid transport in physically and geochemically heterogeneous porous media.

    Science.gov (United States)

    Sun, N; Elimelech, M; Sun, N Z; Ryan, J N

    2001-06-01

    A two-dimensional model for colloid transport in geochemically and physically heterogeneous porous media is presented. The model considers patchwise geochemical heterogeneity, which is suitable to describe the chemical variability of many surficial aquifers with ferric oxyhydroxide-coated porous matrix, as well as spatial variability of hydraulic conductivity, which results in heterogeneous flow field. The model is comprised of a transient fluid flow equation, a transient colloid transport equation, and an equation for the dynamics of colloid deposition and release. Numerical simulations were carried out with the model to investigate the colloid transport behavior in layered and randomly heterogeneous porous media. Results demonstrate that physical and geochemical heterogeneities markedly affect the colloid transport behavior. Layered physical or geochemical heterogeneity can result in distinct preferential flow paths of colloidal particles. Furthermore, the combined effect of layered physical and geochemical heterogeneity may result in enhanced or reduced preferential flow of colloids. Random distribution of physical heterogeneity (hydraulic conductivity) results in a random flow field and an irregularly distributed colloid concentration profile in the porous medium. Contrary to random physical heterogeneity, the effect of random patchwise geochemical heterogeneity on colloid transport behavior is not significant. It is mostly the mean value of geochemical heterogeneity rather than its distribution that governs the colloid transport behavior.

  2. Colloidal QDs-polymer nanocomposites

    Science.gov (United States)

    Gordillo, H.; Suárez, I.; Rodríguez-Cantó, P.; Abargues, R.; García-Calzada, R.; Chyrvony, V.; Albert, S.; Martínez-Pastor, J.

    2012-04-01

    Nanometer-size colloidal semiconductor nanocrystals, or Quantum Dots (NQD), are very prospective active centers because their light emission is highly efficient and temperature-independent. Nanocomposites based on the incorporation of QDs inside a polymer matrix are very promising materials for application in future photonic devices because they combine the properties of QDs with the technological feasibility of polymers. In the present work some basic applications of these new materials have been studied. Firstly, the fabrication of planar and linear waveguides based on the incorporation of CdS, CdSe and CdTe in PMMA and SU-8 are demonstrated. As a result, photoluminescence (PL) of the QDs are coupled to a waveguide mode, being it able to obtain multicolor waveguiding. Secondly, nanocomposite films have been evaluated as photon energy down-shifting converters to improve the efficiency of solar cells.

  3. Colloidal gold-based immunochromatographic strip test compromising optimised combinations of anti-S. suis capsular polysaccharide polyclonal antibodies for detection of Streptococcus suis.

    Science.gov (United States)

    Nakayama, Tatsuya; Zhao, Jizi; Takeuchi, Dan; Kerdsin, Anusack; Chiranairadul, Piphat; Areeratana, Prasanee; Loetthong, Phacharaphan; Pienpringam, Anupong; Akeda, Yukihiro; Oishi, Kazunori

    2014-10-15

    A rapid diagnosis kit that detects Streptococcus suis (S. suis) antigens from urine with an immunochromatographic stripe (ICS) test was developed in this study. The ICS test was produced using colloidal gold coated with polyclonal antibodies (pAbs) against S. suis. The pAbs were developed from rabbits immunised with S. suis serotype 2 capsular polysaccharides (CPS). Development of the pAbs was investigated to establish their binding to CPS and to determine the maximum sensitivity of two combination antibodies for the ICS test. The results of the ICS optimisation revealed that the combinations of pAb C-N1 and pAb C-N2 had the highest sensitivity to CPS. The minimum limitation of ICS sensitivity indicated 1.0 × 10(4) colony forming units (CFU) and a CPS concentration of 0.05 µg. The assay time for detection of S. suis antigens is less than 15 min, which is suitable for rapid detection. A cross-reactive test was also conducted, and it detected no other bacteria (Streptococcus pneumoniae, Streptococcus agalactiae, Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae). The cross-reactivity of other serotypes in S. suis was also investigated, and tests for serotypes of 1, 1/2, 3, 4, 5, 6, 7, 8, 9, 14, and 16 were positive. This study presents the first report of a development of an ICS that enables the quantitative detection of streptococcal antigens. The S. suis ICS provides several advantages over other methods, including the speed and simplicity of use. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Visualization of Colloid Deposition and Mobilization During Unsteady and Steady Porewater Flow Through Unsaturated Porous Media.

    Science.gov (United States)

    Saiers, J. E.; Gao, B.; Ryan, J. N.

    2004-12-01

    Mineral colloids that are mobilized from near-surface soils during infiltration events may carry sorptive contaminants through the vadose zone and into drinking-water aquifers. The vadose-zone flux of colloid-associated contaminants depends, in part, on the difference between colloid mobilization rates and deposition rates. Our research is aimed at improving current understanding of colloid effects on subsurface-contaminant transport by identifying the mechanisms that govern colloid mobilization and deposition in unsaturated porous media. We present pore-scale observations of the transport of fluorescent microspheres through transparent flow cells packed with a thin layer of partially saturated sand. These visualization experiments were conducted under steady-flow and transient-flow conditions. In experiments in which the air phase was discontinuous and occurred as insular air bubbles, the negatively charged microspheres accumulated at the air-bubble surface and moved freely about this air-water interface. A fraction of these colloids eventually migrated from the air-water interface to the air-water-solid interface, whereupon their motion stopped. Destruction of the air bubbles during imbibition led to the release of colloids retained previously by the air-water interface, but not to the release of colloids held at the air-water-solid interface. Colloids were also trapped upon entry into dead-end water conduits that split from the primary flow channels. The exchange of colloids and water between a dead zone and primary flow channel was slow under steady flow; however, the reconnection of dead-end zones as moisture content increased during imbibition resulted in the mobilization of large concentrations of colloids. Our findings show that multiple mechanisms govern the deposition and mobilization of colloids in unsaturated porous media and provide direction for refining mathematical models for colloid and colloid-facilitated contaminant transport within the vadose

  5. Colloidal Dancers: Designing networks of DNA-functionalized colloids for non-random walks

    Science.gov (United States)

    Gehrels, Emily W.; Rogers, W. Benjamin; Zeravcic, Zorana; Manoharan, Vinothan N.

    2014-03-01

    We present experimental developments of a system of DNA-functionalized colloidal particles with the goal of creating directed motion (`dancing') along patterned substrates in response to temperature cycling. We take advantage of toehold exchange in the design of the DNA sequences that mediate the colloidal interactions to produce broadened, flat, or even re-entrant binding and unbinding transitions between the particles and substrate. Using this new freedom of design, we devise systems where, by thermal ratcheting, we can externally control the direction of motion and sequence of steps of the colloidal dancer. In comparison to DNA-based walkers, which move autonomously and whose motion is controlled by the substrate, our colloidal dancers respond to external driving, and their motion can be controlled in situ. Our use of DNA-functionalized colloidal particles instead of pure DNA systems also enables walking on the mesoscale in contrast to the molecular length scales previously demonstrated, allowing for the future prospect of directed transport over larger distances.

  6. 76 FR 42395 - Business Conduct Standards for Security-Based Swap Dealers and Major Security-Based Swap...

    Science.gov (United States)

    2011-07-18

    ... dealers marketing swaps and security-based swaps that they knew or should have known to be inappropriate... Business Conduct Standards for Security-Based Swap Dealers and Major Security-Based Swap Participants...-11] RIN 3235-AL10 Business Conduct Standards for Security-Based Swap Dealers and Major Security-Based...

  7. Designing Zirconium Coated Polystyrene Colloids and Application

    Directory of Open Access Journals (Sweden)

    Diana Chira

    2009-01-01

    Full Text Available A simple technique has been developed to prepare core colloids that are modified using zirconium oxychloride, based on heating a solution of core colloid composites, consisting of poly (ethylenimine (PEI and zirconium oxychloride. The interaction of zirconium oxychloride with the polystyrene (PS core colloids has been investigated using Fourier transform-infrared spectroscopy (FT-IR, energy dispersive X-ray spectroscopy (EDX, and scanning electron microscopy (SEM data. FT-IR studies confirm the occurrence of amine groups present in PEI which are oxidized to carboxyl groups after the reaction. The EDX data and the SEM images confirm the presence of zirconium particles immobilized on the polystyrene surfaces. Demeton, a highly toxic nerve agent, was used due to its ability to easily bind through its organophosphate group illustrating a practical application of the PS-PEI-Zr particles. Attenuated Total Reflection (ATR Spectroscopy was used to assess the interactions between the toxic nerve agent demeton-S and the PS-PEI-Zr particles. The results show that the presented technique for coating polystyrene core colloids with zirconium was successfully accomplished, and the newly formed particles easily bond with demeton agents through the P=O functional group.

  8. Assembly of Colloidal Materials Using Bioadhesive Interactions

    Science.gov (United States)

    Hammer, Daniel A.; Hiddessen, Amy L.; Tohver, Valeria; Crocker, John C.; Weitz, David A.

    2002-01-01

    We have pursued the use of biological crosslinking molecules of several types to make colloidal materials at relatively low volume fraction of colloidal particles. The objective is to make binary alloys of colloidal particles, made of two different colloidal particles coated with complementary biological lock-and-key binding molecules, which assemble due to the biological specificity. The long-term goal is to use low affinity lock-and-key biological interactions, so that the can anneal to form crystalline states. We have used a variety of different surface chemistries in order to make colloidal materials. Our first system involved using selectin-carbohydrate (sialyl-Lewis) interactions; this chemistry is derived from immune system. This chemical interaction is of relatively low affinity, with timescales for dissociation of several seconds. Furthermore, the adhesion mediated by these molecules can be reversed by the chelation of calcium atoms; thus assembled structures can be disassembled reversibly. Our second system employed avidin-biotin chemistry. This well-studied system is of high affinity, and is generally irreversible on a laboratory time-scale. Thus, we would expect selectin-carbohydrate interactions at high molecular density and avidin-biotin interactions to give kinetically-trapped structures; however, at low densities, we would expect significant differences in the structure and dynamics of the two materials, owing to their very different release rates. We have also begun to use a third chemistry - DNA hybridization. By attaching single stranded DNA oligonucleotide chains to beads, we can drive the assembly of colloidal materials by hybridization of complementary DNA chains. It is well known that DNA adenosine-thymine (A-T) and guanine-cytosine (G-C) bases hybridize pairwise with a Gibbs free energy change of 1.7 kcal/mol per base; thus, the energy of the assembly can be modulated by altering the number of complementary bases in the DNA chains. Using

  9. Influence of colloids on the attenuation and transport of phosphorus in alluvial gravel aquifer and vadose zone media.

    Science.gov (United States)

    Pang, Liping; Lafogler, Mark; Knorr, Bastian; McGill, Erin; Saunders, Darren; Baumann, Thomas; Abraham, Phillip; Close, Murray

    2016-04-15

    Phosphorous (P) leaching (e.g., from effluents, fertilizers) and transport in highly permeable subsurface media can be an important pathway that contributes to eutrophication of receiving surface waters as groundwater recharges the base-flow of surface waters. Here we investigated attenuation and transport of orthophosphate-P in gravel aquifer and vadose zone media in the presence and absence of model colloids (Escherichia coli, kaolinite, goethite). Experiments were conducted using repacked aquifer media in a large column (2m long, 0.19m in diameter) and intact cores (0.4m long, 0.24m in diameter) of vadose zone media under typical field flow rates. In the absence of the model colloids, P was readily traveled through the aquifer media with little attenuation (up to 100% recovery) and retardation, and P adsorption was highly reversible. Conversely, addition of the model colloids generally resulted in reduced P concentration and mass recovery (down to 28% recovery), and increased retardation and adsorption irreversibility in both aquifer and vadose zone media. The degree of colloid-assisted P attenuation was most significant in the presence of fine material and Fe-containing colloids at low flow rate but was least significant in the presence of coarse gravels and E. coli at high flow rate. Based on the experimental results, setback distances of 49-53m were estimated to allow a reduction of P concentrations in groundwater to acceptable levels in the receiving water. These estimates were consistent with field observations in the same aquifer media. Colloid-assisted P attenuation can be utilized to develop mitigation strategies to better manage effluent applications in gravelly soils. To efficiently retain P within soil matrix and reduce P leaching to groundwater, it is recommended to select soils that are rich in iron oxides, to periodically disturb soil preferential flow paths by tillage, and to apply a low irrigation rate. Copyright © 2016 Elsevier B.V. All rights

  10. Colloid-borne forms of tetravalent actinides: a brief review.

    Science.gov (United States)

    Zänker, Harald; Hennig, Christoph

    2014-02-01

    Tetravalent actinides, An(IV), are usually assumed to be little mobile in near-neutral environmental waters because of their low solubility. However, there are certain geochemical scenarios during which mobilization of An(IV) in a colloid-borne (waterborne) form cannot be ruled out. A compilation of colloid-borne forms of tetravalent actinides described so far for laboratory experiments together with several examples of An(IV) colloids observed in field experiments and real-world scenarios are given. They are intended to be a knowledge base and a tool for those who have to interpret actinide behavior under environmental conditions. Synthetic colloids containing structural An(IV) and synthetic colloids carrying adsorbed An(IV) are considered. Their behavior is compared with the behavior of An(IV) colloids observed after the intentional or unintentional release of actinides into the environment. A list of knowledge gaps as to the behavior of An(IV) colloids is provided and items which need further research are highlighted. Copyright © 2013 Elsevier B.V. All rights reserved.

  11. Stochastic Simulations of Colloid-Facilitated Transport for Long Time and Space Scales

    Science.gov (United States)

    Painter, S.; Pickett, D.; Cvetkovic, V.

    2004-12-01

    Although it is widely recognized that naturally occurring inorganic colloids can potentially enhance the transport of radionuclides in the subsurface, comparatively few analyses have considered the long times and large travel distances associated with potential nuclear waste repositories. One-dimensional transient simulations in a stochastic Lagrangian framework are used to explore model and parameter sensitivities for colloid-facilitated transport at large scales. The model accounts for (i) advection and dispersion of radionuclides and colloids, (ii) radionuclide decay, (iii) exchange of radionuclides among colloid-bound, dissolved, and fixed substrate phases, and (iv) attachment and detachment of colloids to the fixed substrate. Kinetics of the exchanges between dissolved and colloid-bound states are addressed using linear and non-linear models. Generic sensitivity studies addressing both fractured and granular aquifers are considered, as is an example based on the groundwater transport pathway for the potential repository at Yucca Mountain, Nevada. In the absence of mitigating factors such as permanent filtration of colloids, transport may be enhanced over the situation without colloids, but only for strongly sorbing radionuclides. Mass transfer between solution and immobilized colloids makes colloid retardation relatively ineffective at reducing facilitated transport except when the retardation factor is large. Results are particularly sensitive to the rate of desorption from colloids, a parameter that is difficult to measure with short-duration experiments. This paper is an independent product of the CNWRA and does not necessarily reflect the view or regulatory position of the U.S. Nuclear Regulatory Commission.

  12. Model simulations of particle aggregation effect on colloid exchange between streams and streambeds.

    Science.gov (United States)

    Areepitak, Trachu; Ren, Jianhong

    2011-07-01

    Colloids found in natural streams have large reactive surface areas, which makes them significant absorbents and carriers for pollutants. Stream-subsurface exchange plays a critical role in regulating the transport of colloids and contaminants in natural streams. Previous process-based multiphase exchange models were developed without consideration of colloid-colloid interaction. However, many studies have indicated that aggregation is a significant process and needs to be considered in stream process analysis. Herein, a new colloid exchange model was developed by including particle aggregation in addition to colloid settling and filtration. Self-preserving size distribution concepts and classical aggregation theory were employed to model the aggregation process. Model simulations indicate that under conditions of low filtration and high degree of particle-particle interaction, aggregation could either decrease or increase the amount of colloids retained in streambeds, depending on the initial particle size. Thus, two possible cases may occur including enhanced colloid deposition and facilitated colloid transport. Also, when the aggregation rate is high and filtration increases, more particles are retained by bed sediments due to filtration, and fewer are aggregated, which reduces the extent of aggregation effect on colloid deposition. The work presented here will contribute to a better understanding and prediction of colloid transport phenomena in natural streams.

  13. Cracking in Drying Colloidal Films

    Science.gov (United States)

    Singh, Karnail B.; Tirumkudulu, Mahesh S.

    2007-05-01

    It has long been known that thick films of colloidal dispersions such as wet clays, paints, and coatings crack under drying. Although capillary stresses generated during drying have been recently identified as the cause for cracking, the existence of a maximum crack-free film thickness that depends on particle size, rigidity, and packing has not been understood. Here, we identify two distinct regimes for crack-free films based on the magnitude of compressive strain at the maximum attainable capillary pressure and show remarkable agreement of measurements with our theory. We anticipate our results to not only form the basis for design of coating formulations for the paints, coatings, and ceramics industry but also assist in the production of crack-free photonic band gap crystals.

  14. Polymers and colloids

    Energy Technology Data Exchange (ETDEWEB)

    Schurtenberger, P. [ETH Zurich, Inst. fuer Polymere, Zurich (Switzerland)

    1996-11-01

    A wealth of structural information from colloid and polymer solutions on a large range of length scales can be obtained using small angle neutron scattering (SANS) experiments. After a general introduction to the field of soft condensed matter, I shall give a few selected examples on how SANS combined with suitable contrast variation schemes can be used to extract information on the size and conformation of polymer coils in solution and in the melt, and on the local structure and flexibility of polymerlike micelles and microemulsions. (author) 8 figs., tabs., 44 refs.

  15. Neutron scattering from colloids

    International Nuclear Information System (INIS)

    Cebula, D.J.; Thomas, R.K.; Harris, N.M.; Tabony, J.; White, J.W.

    1978-01-01

    This paper appraises the usefulness of neutron diffraction and small angle scattering for determining the structure of dilute and concentrated sols. For monodisperse polystyrene latex, the particle size and density can be readily determined and an upper limit to density fluctuations within the colloid particle set. For the polystyrene latex peptized by the adsorption of laurate, the physical dimensions and packing density of the adsorbed phase can be determined. The effects of polydispersity for unpeptized and peptized graphite sols, and the effects of extreme particle anisotropy using sols of montmorillonite clay minerals have been studied. (author)

  16. Nematic Liquid-Crystal Colloids

    Science.gov (United States)

    Muševič, Igor

    2017-01-01

    This article provides a concise review of a new state of colloidal matter called nematic liquid-crystal colloids. These colloids are obtained by dispersing microparticles of different shapes in a nematic liquid crystal that acts as a solvent for the dispersed particles. The microparticles induce a local deformation of the liquid crystal, which then generates topological defects and long-range forces between the neighboring particles. The colloidal forces in nematic colloids are much stronger than the forces in ordinary colloids in isotropic solvents, exceeding thousands of kBT per micrometer-sized particle. Of special interest are the topological defects in nematic colloids, which appear in many fascinating forms, such as singular points, closed loops, multitudes of interlinked and knotted loops or soliton-like structures. The richness of the topological phenomena and the possibility to design and control topological defects with laser tweezers make colloids in nematic liquid crystals an excellent playground for testing the basic theorems of topology. PMID:29295574

  17. Nematic Liquid-Crystal Colloids

    Directory of Open Access Journals (Sweden)

    Igor Muševič

    2017-12-01

    Full Text Available This article provides a concise review of a new state of colloidal matter called nematic liquid-crystal colloids. These colloids are obtained by dispersing microparticles of different shapes in a nematic liquid crystal that acts as a solvent for the dispersed particles. The microparticles induce a local deformation of the liquid crystal, which then generates topological defects and long-range forces between the neighboring particles. The colloidal forces in nematic colloids are much stronger than the forces in ordinary colloids in isotropic solvents, exceeding thousands of kBT per micrometer-sized particle. Of special interest are the topological defects in nematic colloids, which appear in many fascinating forms, such as singular points, closed loops, multitudes of interlinked and knotted loops or soliton-like structures. The richness of the topological phenomena and the possibility to design and control topological defects with laser tweezers make colloids in nematic liquid crystals an excellent playground for testing the basic theorems of topology.

  18. Direct visualization of colloidal liquids

    Science.gov (United States)

    Durand, Richard Vernon

    We have investigated various colloidal systems consisting of aqueous suspensions of micron sized polystyrene particles. These systems are appealing because they provide a fertile testing ground for theories of both the liquid and solid states, as well as for theories describing hydrodynamic interactions. Our first study of colloidal systems was motivated by some interesting observations we made while looking at a suspension under a light microscope. We, as well as other workers, noticed that particles undergoing Brownian motion can appear to linger around each other for long periods of time. The question arose as to whether this lingering was a product of interparticle interactions, or was an artifact due to random thermal motion and projection onto a two dimensional image plane. We found that the latter was true, which drove home the idea that we must be wary of our own biases when making scientific observations. During the course of the research on this lingering behavior, we developed a mathematical technique for generating successively more accurate approximate analytical solutions to initial value linear partial differential equations which are first order in time and have no mixing of spatial and time derivatives. This formalism is especially useful for diffusion problems, since the analytical approximation conserves probability at each order of approximation. Our next experimental effort involved colloidal systems in which the suspending medium was carefully prepared to promote long ranged electrostatic interactions between the particles. The interaction potential in such a suspension has been the topic of much research recently. Using digital video microscopy, as well as techniques we developed allowing the proper analysis of two dimensional data, we found that the interaction length in our samples was surprisingly short ranged compared to what we expected based on our water purification experiments. The problems with projection effects associated with two

  19. Interfacial colloidal rod dynamics: Coefficients, simulations, and analysis

    Science.gov (United States)

    Yang, Yuguang; Bevan, Michael A.

    2017-08-01

    Colloidal rod diffusion near a wall is modeled and simulated based on a constrained Stokesian dynamic model of chains-of-spheres. By modeling colloidal rods as chains-of-spheres, complete diffusion tensors are computed for colloidal rods in bulk media and near interfaces, including hydrodynamic interactions, translation-rotation coupling, and all diffusion modes in the particle and lab frames. Simulated trajectories based on the chain-of-spheres diffusion tensor are quantified in terms of typical experimental quantities such as mean squared positional and angular displacements as well as autocorrelation functions. Theoretical expressions are reported to predict measured average diffusivities as well as the crossover from short-time anisotropic translational diffusion along the rod's major axis to isotropic diffusion. Diffusion modes are quantified in terms of closed form empirical fits to model results to aid their use in interpretation and prediction of experiments involving colloidal rod diffusion in interfacial and confined systems.

  20. Colloidal motion under the action of a thermophoretic force.

    Science.gov (United States)

    Burelbach, Jerome; Zupkauskas, Mykolas; Lamboll, Robin; Lan, Yang; Eiser, Erika

    2017-09-07

    We present thermophoretic measurements in aqueous suspensions of three different polystyrene (PS) particles of varying negative charge, size, and surface coating. Our measurement technique is based on the observation of the colloidal steady-state distribution using conventional bright-field microscopy, which avoids undesirable effects such as laser-induced convection or local heating. We find that the colloids with the weakest zeta potential exhibit the strongest thermophoretic effect, suggesting that the Soret coefficient has a more intricate dependence on surface functionality than predicted by existing theoretical approaches. We also study the relaxation of the colloids to steady-state and propose a model to quantify the relaxation speed, based on the time evolution of the colloidal center of mass. Our observations are well described by this model and show that the relaxation speed tends to increase with the magnitude of the thermophoretic force.

  1. Hysteresis in the amount of colloids mobilized from intact cores of a fractured soil as a result of changes in the ionic strength of simulated rainfall

    Science.gov (United States)

    Mohanty, S.; Ryan, J. N.; Saiers, J. E.

    2010-12-01

    Understanding the mechanisms of colloid mobilization is essential to predicting the importance of colloid-facilitated transport of contaminants in subsurface environment. The mobilization of colloids increases with a decrease in the ionic strength of the pore water. Colloid mobilization is hysteretic in response to changes in ionic strength - the amount of colloids mobilized at a given ionic strength is not matched when the experiment is repeated following exposure to pore water of higher or lower ionic strengths. An exchange of pore water between the soil matrix and macropores is proposed to be the primary reason for the hysteresis of colloid mobilization during changes in ionic strength. The mobilization of colloids by pore water of a given ionic strength is either enhanced or inhibited by the slow release of matrix pore water of a lower or higher ionic strengths, respectively. This hypothesis was tested by conducting simulated rainfall experiments on undisturbed, intact cores of fractured soil (25.4 cm diameter, 15.2 cm depth) sampled from Oak Ridge National Laboratory, Tennessee. Rainfall of increasing, and then decreasing, ionic strength was applied to soil cores in successive events of 6 h of rainfall and an 18 h pause for each ionic strength. The ionic strength ranged from 0.01 to 10 mM as sodium chloride. Sodium bromide was included to provide a conservative tracer (Br-). Samples were collected from 19 ports in a hexagonal grid at the base of the soil core to identify regions of fast and slow flow attributed to macropore and matrix pathways. The samples were analyzed for concentrations of colloids (turbidity) and bromide (ion-selective electrode), conductivity, and pH. A flow-interruption method during bromide injection was employed to estimate the mass transfer rate of bromide between the soil macropores and matrix. Colloid concentrations, flow rates, and breakthrough times for bromide were found to be different for each port in the experiments at

  2. Hybrid Drug Delivery Patches Based on Spherical Cellulose Nanocrystals and Colloid Titania—Synthesis and Antibacterial Properties

    Directory of Open Access Journals (Sweden)

    Olga L. Evdokimova

    2018-04-01

    Full Text Available Spherical cellulose nanocrystal-based hybrids grafted with titania nanoparticles were successfully produced for topical drug delivery. The conventional analytical filter paper was used as a precursor material for cellulose nanocrystals (CNC production. Cellulose nanocrystals were extracted via a simple and quick two-step process based on first the complexation with Cu(II solution in aqueous ammonia followed by acid hydrolysis with diluted H2SO4. Triclosan was selected as a model drug for complexation with titania and further introduction into the nanocellulose based composite. Obtained materials were characterized by a broad variety of microscopic, spectroscopic, and thermal analysis methods. The drug release studies showed long-term release profiles of triclosan from the titania based nanocomposite that agreed with Higuchi model. The bacterial susceptibility tests demonstrated that released triclosan retained its antibacterial activity against Escherichia coli and Staphylococcus aureus. It was found that a small amount of titania significantly improved the antibacterial activity of obtained nanocomposites, even without immobilization of model drug. Thus, the developed hybrid patches are highly promising candidates for potential application as antibacterial agents.

  3. Optimizing colloidal nanocrystals for applications

    International Nuclear Information System (INIS)

    Sytnyk, M.

    2015-01-01

    In the scientific literature colloidal nanocrystals are presented as promising materials for multiple applications, in areas covering optoelectronics, photovoltaics, spintronics, catalysis, and bio-medicine. On the marked are, however, only a very limited number of examples found, indeed implementing colloidal nanocrystals. Thus the scope of this thesis was to modify nanocrystals and to tune their properties to fulfill specific demands. While some modifications could be achieved by post synthetic treatments, one key problem of colloidal nanocrystals, hampering there widespread application is the toxicity of their constituents. To develop nanocrystals from non-toxic materials has been a major goal of this thesis as well. Roughly, the results in this thesis could be subdivided into three parts: (i) the development of ion exchange methods to tailor the properties of metallic and metal-oxide based nanocrystal heterostructures, (ii), the synthesis of semiconductor nanocrystals from non-toxic materials, and (iii) the characterization of the nanocrystals by measurements of their morphology, chemical composition, magnetic-, optical-, and electronic properties. In detail, the thesis is subdivided into an introductory chapter, 4 chapters reporting on scientific results, a chapter reporting the used methods, and the conclusions. The 4 chapters devoted to the scientific results correspond to manuscripts, which are either currently in preparation, or have been published in highly ranked scientific journals such as NanoLetters (chapter 2), ACS Nano (chapter 4), or JACS (chapter 5). Thus, these chapters provide also an extra introduction and conclusion section, as well as separate reference lists. Chapter 2 describes a cation exchange process which is used to tune and improve the magnetic properties of different iron-oxide based colloidal nanocrystal-heterostructures. The superparamagnetic blocking temperature, magnetic remanence, and coercivity is tuned by replacing Fe2+ by Co2

  4. Pore water colloid properties in argillaceous sedimentary rocks

    OpenAIRE

    Degueldre, Claude; Cloet, Veerle

    2016-01-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions ...

  5. Silica-coated titania and zirconia colloids for subsurface transport field experiments

    Science.gov (United States)

    Ryan, Joseph N.; Elimelech, Menachem; Baeseman, Jenny L.; Magelky, Robin D.

    2000-01-01

    Silica-coated titania (TiO2) and zirconia (ZrO2) colloids were synthesized in two sizes to provide easily traced mineral colloids for subsurface transport experiments. Electrophoretic mobility measurements showed that coating with silica imparted surface properties similar to pure silica to the titania and zirconia colloids. Measurements of steady electrophoretic mobility and size (by dynamic light scattering) over a 90-day period showed that the silica-coated colloids were stable to aggregation and loss of coating. A natural gradient field experiment conducted in an iron oxide-coated sand and gravel aquifer also showed that the surface properties of the silica-coated colloids were similar. Colloid transport was traced at μg L-1 concentrations by inductively coupled plasma-atomic emission spectroscopy measurement of Ti and Zr in acidified samples.

  6. Magneto-acousto-electrical Measurement Based Electrical Conductivity Reconstruction for Tissues.

    Science.gov (United States)

    Zhou, Yan; Ma, Qingyu; Guo, Gepu; Tu, Juan; Zhang, Dong

    2018-05-01

    Based on the interaction of ultrasonic excitation and magnetoelectrical induction, magneto-acousto-electrical (MAE) technology was demonstrated to have the capability of differentiating conductivity variations along the acoustic transmission. By applying the characteristics of the MAE voltage, a simplified algorithm of MAE measurement based conductivity reconstruction was developed. With the analyses of acoustic vibration, ultrasound propagation, Hall effect, and magnetoelectrical induction, theoretical and experimental studies of MAE measurement and conductivity reconstruction were performed. The formula of MAE voltage was derived and simplified for the transducer with strong directivity. MAE voltage was simulated for a three-layer gel phantom and the conductivity distribution was reconstructed using the modified Wiener inverse filter and Hilbert transform, which was also verified by experimental measurements. The experimental results are basically consistent with the simulations, and demonstrate that the wave packets of MAE voltage are generated at tissue interfaces with the amplitudes and vibration polarities representing the values and directions of conductivity variations. With the proposed algorithm, the amplitude and polarity of conductivity gradient can be restored and the conductivity distribution can also be reconstructed accurately. The favorable results demonstrate the feasibility of accurate conductivity reconstruction with improved spatial resolution using MAE measurement for tissues with conductivity variations, especially suitable for nondispersive tissues with abrupt conductivity changes. This study demonstrates that the MAE measurement based conductivity reconstruction algorithm can be applied as a new strategy for nondestructive real-time monitoring of conductivity variations in biomedical engineering.

  7. Equivalent conductivity method: straightforward analytical solution for metasurface-based structures

    DEFF Research Database (Denmark)

    Danaeifar, Mohammad; Granpayeh, Nosrat; Mortensen, N. Asger

    2015-01-01

    We present an equivalent conductivity method for analyzing metasurface-based structures, which relies on the derivation of equivalent conductivity containing the properties such as the geometry, periodicity, and the surrounding materials. Using this approach, one can calculate the equivalent....... This method is further applied to design graphene-based mid-infrared absorbers, and the results obtained by the equivalent conductivity method are confirmed by full-wave simulations....

  8. Aggregation-based colorimetric sensor for determination of prothioconazole fungicide using colloidal silver nanoparticles (AgNPs)

    Science.gov (United States)

    Ivrigh, Zahra Jafar-Nezhad; Fahimi-Kashani, Nafiseh; Hormozi-Nezhad, M. Reza

    2017-12-01

    There is a growing interest in developing high-performance sensors monitoring fungicides, due to their broadly usage and their adverse effects on humans and wildlife. In the present study, a colorimetric probe has been proposed for detection of prothioconazole based on aggregation of unmodified silver nanoparticles (AgNPs). Under optimized condition, linear relationships between the concentration of prothioconazole and the absorbance ratio of A500/A395 were found over the range of 0.01 μg·mL- 1 to 0.4 μg·mL- 1 with quantification limit as low as 1.7 ng·mL- 1. Furthermore, AgNPs color change from yellow to pink-orange in presence of prothioconazole, indicates highly sensitive naked-eye colorimetric assay for quantifying prothioconazole in real applications. The proposed approach was successfully used for the determination of prothioconazole in wheat flour and paddy water sample.

  9. Experimental analysis of colloid capture by a cylindrical collector in laminar overland flow.

    Science.gov (United States)

    Wu, Lei; Gao, Bin; Muñoz-Carpena, Rafael

    2011-09-15

    Although colloid-facilitated contaminant transport in water flow is a well-known contamination process, little research has been conducted to investigate the transport of colloidal particles through emergent vegetation in overland flow. In this work, a series of laboratory experiments were conducted to measure the single-collector contact efficiency (η(0)) of colloid capture by a simulated plant stem in laminar lateral flow. Fluorescent microspheres of various sizes were used as experimental colloids. The colloid suspensions were applied to a glass cylinder installed in a small size flow chamber at different flow rates. Two cylinder sizes were tested in the experiment and silicone grease was applied to the cylinder surface to make it favorable for colloid deposition. Our results showed that increases in flow rate and collector size reduced the value of η(0) and a minimum value of η(0) might exist for a colloid size. The experimental data were compared to theoretical predictions of different single-collector contact efficiency models. The results indicated that existing single-collector contact efficiency models underestimated the η(0) of colloid capture by the cylinders in laminar overland flow. A regression equation of η(0) as a function of collector Reynolds number (Re(c)) and Peclet number (N(Pe)) was developed and fit the experimental data very well (R(2) > 0.98). This regression equation can be used to help construct and refine mathematical models of colloid transport and filtration in laminar overland flow on vegetated surfaces.

  10. Colloidal gold nanoparticle probe-based immunochromatographic assay for the rapid detection of chromium ions in water and serum samples

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xi; Xiang, Jun-Jian; Tang, Yong; Zhang, Xiao-Li; Fu, Qiang-Qiang; Zou, Jun-Hui; Lin, Yuehe

    2012-09-01

    An immunochromatographic assay (ICA) using gold nanoparticles coated with monoclonal antibody (McAb) for the detection of chromium ions (Cr) in water and serum samples was developed, optimized, and validated. Gold nanoparticles coated with affinity- purified monoclonal antibodies against isothiocyanobenzyl-EDTA (iEDTA)-chelated Cr3+ were used as the detecting reagent in this completive immunoassay-based one- step test strip. The ICA was investigated to measure chromium speciation in water samples. Chromium standard samples of 0-80 ng/mL in water were determined by the test strips. The results showed that the visual lowest detection limit (LDL) of the test strip was 50.0 ng/mL. A portable colorimetric lateral flow reader was used for the quantification of Cr. The results indicated that the linear range of the ICA with colorimetric detection was 5-80 ng/mL. The ICA was also validated for the detection of chromium ions in serum samples. The test trips showed high stability in that they could be stored at at 37 C for at least 12 weeks without significant loss of activity. The test strip also showed good selectivity for Cr detection with negligible interference from other heavy metals. Because of its low cost and short testing time (within 5 min), the test strip is especially suitable for on-site large- scale screening of Cr-polluted water samples, biomonitoring of Cr exposure, and many other field applications.

  11. Development of a colloidal gold immunochromatographic strip based on HSP70 for the rapid detection of Echinococcus granulosus in sheep.

    Science.gov (United States)

    Zhuo, Xunhui; Yu, Yingchao; Chen, Xueqiu; Zhang, Zhuangzhi; Yang, Yi; Du, Aifang

    2017-06-15

    Echinococcus granulosus is the causative pathogen of cystic echinococcosis, a serious disease endangering human and animal health. In this study, an immunochromatographic strip was developed based on the recombinant protein Heat shock protein 70 (HSP70) for the serological detection of E. granulosus. The protocol completes within 20min requiring no specialized equipment or chemical reagents, while specificity tests confirmed no cross-reactivity with positive serum of Fasciola hepatica, Haemonchus contortus, Peste des petits ruminants virus (PPRV) and Foot-and-mouth disease virus (FMDV). The strips remained stable after storage at 4°C for up to 8 months. Both immunochromatographic strip and ELISA tests were applied to detect E. granulosus antibody in a total of 728 serum samples obtained from slaughter houses in Zhejiang Province. Our data revealed positive rates of 2.61 and 1.65% by immunochromatographic strip and ELISA methods, respectively. The immunochromatographic strip test developed in this study provides a simple, specific and rapid method of E. granulosus antibody detection and infected sheep monitoring. Copyright © 2017. Published by Elsevier B.V.

  12. Use of anionic surfactants for selective polishing of silicon dioxide over silicon nitride films using colloidal silica-based slurries

    Science.gov (United States)

    Penta, Naresh K.; Amanapu, H. P.; Peethala, B. C.; Babu, S. V.

    2013-10-01

    Four different anionic surfactants, sodium dodecyl sulfate, dodecyl benzene sulfonic acid (DBSA), dodecyl phosphate and Sodium lauroyl sarcosine, selected from the sulfate, phosphate, and carboxylic family, were investigated as additives in silica dispersions for selective polishing of silicon dioxide over silicon nitride films. We found that all these anionic surfactants suppress the nitride removal rates (RR) for pH ≤4 while more or less maintaining the oxide RRs, resulting in high oxide-to-nitride RR selectivity. The RR data obtained as a function of pH were explained based on pH dependent distributions of surfactant species, change in the zeta potentials of oxide and nitride surfaces, and thermogravimetric data. It appears that the negatively charged surfactant species preferentially adsorb on the positively charged nitride surface below IEP through its electrostatic interactions and form a bilayer adsorption, resulting in the suppression of nitride RRs. In contrast to the surfactants, K2SO4 interacts only weakly with the nitride surface and hence cannot suppress its RR.

  13. Liquid crystal boojum-colloids

    International Nuclear Information System (INIS)

    Tasinkevych, M; Silvestre, N M; Telo da Gama, M M

    2012-01-01

    Colloidal particles dispersed in a liquid crystal (LC) lead to distortions of the director field. The distortions are responsible for long-range effective colloidal interactions whose asymptotic behaviour is well understood. The short-distance behaviour depends on the structure and dynamics of the topological defects nucleated near the colloidal particles and a full nonlinear theory is required to describe it. Spherical colloidal particles with strong planar degenerate anchoring nucleate a pair of antipodal surface topological defects, known as boojums. We use the Landau-de Gennes theory to resolve the mesoscopic structure of the boojum cores and to determine the pairwise colloidal interactions. We compare the results in three (3D) and two (2D) spatial dimensions for spherical and disc-like colloidal particles, respectively. The corresponding free energy functionals are minimized numerically using finite elements with adaptive meshes. Boojums are always point-like in 2D, but acquire a rather complex structure in 3D, which depends on the combination of the anchoring potential, the radius of the colloid, the temperature and the LC elastic anisotropy. We identify three types of defect cores in 3D that we call single, double and split-core boojums, and investigate the associated structural transitions. The split-core structure is favoured by low temperatures, strong anchoring and small twist to splay or bend ratios. For sufficiently strong anchoring potentials characterized by a well-defined uniaxial minimum, the split-core boojums are the only stable configuration. In the presence of two colloidal particles, we observe substantial re-arrangements of the inner defects in both 3D and 2D. These re-arrangements lead to qualitative changes in the force-distance profile when compared to the asymptotic quadrupole-quadrupole interaction. In line with the experimental results, the presence of the defects prevents coalescence of the colloidal particles in 2D, but not in 3D

  14. Acoustic separation of oil droplets, colloidal particles and their mixtures in a microfluidic cell

    KAUST Repository

    Vakarelski, Ivan Uriev

    2016-06-15

    Here we report direct macroscopic and microscopic observations of acoustic driven separation of dodecane oil droplets in water in the presence and absence of colloidal silica particles suspended in the water phase. The experiments were conducted in a simple rectangular channel glass microfluidic cell in which an ultrasound standing wave pattern was generated at 300 KHz frequency. The separation process of both oil droplets and colloidal particles inside the cell was recorded using a high-speed video camera equipped with a macro-objective lens for macroscopic observation or with a high-speed camera attached to an inverted optical microscope for a higher resolution microscopic observation. We characterize the clustering process in the case of emulsion droplets or solid colloidal particles and ultimately demonstrate the emulsion droplets separation from the solid particles in the mixtures based on their different acoustic contrast factors. Finally, we conduct proof of concept experiment to show that the same approach can be used in a continuous fluid flow process.

  15. Structural and ionic conductivity studies on proton conducting solid biopolymer electrolyte based on 2hydroxyethyl cellulose incorporated DTAB

    Science.gov (United States)

    Ahmad, N. H.; Bakar, N. Y.; Isa, M. I. N.

    2017-09-01

    Solid biopolymer electrolytes (SBEs) based on 2hydroxyethyl cellulose (2HEC) complexes with dodecyltrimethyl ammonium bromide (DTAB) salt in various composition (wt. %) were successfully prepared by using solution casting technique. The ion - polymer interaction and structural studies have been reported by Fourier transform infrared spectroscopy (FTIR) supported with X - ray diffraction (XRD) and Electrical impedance spectroscopy (EIS). FTIR spectral shows interaction of 2HEC with DTAB happen at peak 2914cm-1, 2848cm-1, 2353cm-1, 2328cm-1, 1720cm-1, 1437cm-1, 1344cm-1, 1198cm-1 1095cm-1 1051cm-1, 912cm-1 and 872cm-1. The interaction of complexes leads to an increase in number of ion jump into neighboring vacant sites until it reaches the highest conductivity at room temperature which is 2.80 x 10-5 Scm-1 for sample containing 9wt. % of DTAB. The temperature dependence of the SBEs system exhibits Arrhenius behavior and the XRD spectral analysis shows the higher salt loading the crystallinity of the SBEs which also increased.

  16. Chancellor Water Colloids: Characterization and Radionuclide Associated Transport

    Energy Technology Data Exchange (ETDEWEB)

    Reimus, Paul William [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Boukhalfa, Hakim [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-09-26

    Column transport experiments were conducted in which water from the Chancellor nuclear test cavity was transported through crushed volcanic tuff from Pahute Mesa. In one experiment, the cavity water was spiked with solute 137Cs, and in another it was spiked with 239/240Pu(IV) nanocolloids. A third column experiment was conducted with no radionuclide spike at all, although the 137Cs concentrations in the water were still high enough to quantify in the column effluent. The radionuclides strongly partitioned to natural colloids present in the water, which were characterized for size distribution, mass concentration, zeta potential/surface charge, critical coagulation concentration, and qualitative mineralogy. In the spiked water experiments, the unanalyzed portion of the high-concentration column effluent samples were combined and re-injected into the respective columns as a second pulse. This procedure was repeated again for a third injection. Measurable filtration of the colloids was observed after each initial injection of the Chancellor water into the columns, but the subsequent injections (spiked water experiments only) exhibited no apparent filtration, suggesting that the colloids that remained mobile after relatively short transport distances were more resistant to filtration than the initial population of colloids. It was also observed that while significant desorption of 137Cs from the colloids occurred after the first injection in both the spiked and unspiked waters, subsequent injections of the spiked water exhibited much less 137Cs desorption (much greater 137Cs colloid-associated transport). This result suggests that the 137Cs that remained associated with colloids during the first injection represented a fraction that was more strongly adsorbed to the mobile colloids than the initial 137Cs associated with the colloids. A greater amount of the 239/240

  17. The effect of flow heterogeneity on the mobilization of colloids from metal-contaminated soils

    Science.gov (United States)

    Denovio, N. M.; Ryan, J. N.

    2003-12-01

    In vadose zone soils, colloid-facilitated transport has been shown to play a significant role in contaminant transport because colloids are abundant and the kinetics of contaminant desorption are likely to be slow relative to the time scale for colloid transport through the unsaturated zone. Understanding the rate of colloid generation and transport with respect to the surface area available for contaminant sorption and chemical composition of these colloids is critical for predicting colloid-facilitated transport. Soil cores (approximately 20 cm3)obtained from the Arkansas River Valley in Leadville, Colorado, where there is significant metal contamination, were leached at three rainfall rates corresponding to 10-, 20-, and 100-year storm events. Effluent water samples were collected with a 2.5 cm spatial resolution at the base of the column. Samples were analyzed for colloid concentration, size and metal elements (Pb, Zn, Cu) in addition to Al, Si, and other metals. Despite significant variability in the spatial distribution of water flow, there was little to no variability in the rate of colloid generation, size of the colloids, or heavy metal generation within a time step. Generally, colloid size appeared to increase during the course of the experiments and greater concentrations of heavy metals were generated with increasing duration of each rainfall event.

  18. Secondary and Primary Energy Minimum Interactions of Colloids in Porous Media: A Novel Binomial Modeling Approach

    Science.gov (United States)

    Hilpert, M.; Rasmuson, J. A.; Johnson, W. P.

    2016-12-01

    Aqueous transport of colloids in porous media is significantlyaffected by interactions with grain surfaces associated with theprimary and secondary energy minimum at colloid-surface separationdistances within a few to hundreds of nanometers, respectively. Nearsurface fluid domain colloids experience relatively low fluid drag andrelatively strong colloidal forces that slow their down-gradienttranslation relative to colloids in bulk fluid. Near surface fluiddomain colloids may re-enter into the bulk fluid via diffusion(nanoparticles) or expulsion at rear flow stagnation zones, or theymay immobilize (attach) via strong primary minimum interactions.Our new model accounts for all possible permutations of mass transferwithin a dual pore and grain network. The primary phenomena therebyrepresented in the model are mass transfer of colloids between thebulk and near-surface fluid domains and immobilization. A previouslydeveloped pore-scale model provides likelihoods and time scalesassociated with the above pore-scale colloid mass transfer processes,whereas the network-scale model employs fluid flow field and graintopology to determine probabilities of transfer from up-gradient bulkand near-surface fluid domains to down-gradient bulk and near-surfacefluid domains. We used the model to make predictions of colloid fateand transport at the column scale based on independently determinedpore-scale parameterizations. The models allows separating theeffects of hydrodynamic dispersion and colloid attachment anddetachment on breakthrough elution curves.

  19. Hybrid colloidal plasmonic-photonic crystals.

    Science.gov (United States)

    Romanov, Sergei G; Korovin, Alexander V; Regensburger, Alois; Peschel, Ulf

    2011-06-17

    We review the recently emerged class of hybrid metal-dielectric colloidal photonic crystals. The hybrid approach is understood as the combination of a dielectric photonic crystal with a continuous metal film. It allows to achieve a strong modification of the optical properties of photonic crystals by involving the light scattering at electronic excitations in the metal component into moulding of the light flow in series to the diffraction resonances occurring in the body of the photonic crystal. We consider different realizations of hybrid plasmonic-photonic crystals based on two- and three-dimensional colloidal photonic crystals in association with flat and corrugated metal films. In agreement with model calculations, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tuneable functionality of these crystals. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Colloidal attraction induced by a temperature gradient.

    Science.gov (United States)

    Di Leonardo, R; Ianni, F; Ruocco, G

    2009-04-21

    Colloidal crystals are of extreme importance for applied research and for fundamental studies in statistical mechanics. Long-range attractive interactions, such as capillary forces, can drive the spontaneous assembly of such mesoscopic ordered structures. However, long-range attractive forces are very rare in the colloidal realm. Here we report a novel strong, long-ranged attraction induced by a thermal gradient in the presence of a wall. By switching the thermal gradient on and off, we can rapidly and reversibly form stable hexagonal 2D crystals. We show that the observed attraction is hydrodynamic in nature and arises from thermally induced slip flow on particle surfaces. We used optical tweezers to measure the force law directly and compare it to an analytical prediction based on Stokes flow driven by Marangoni-like forces.

  1. Ultrasmall colloidal PbS quantum dots

    International Nuclear Information System (INIS)

    Reilly, Nick; Wehrung, Michael; O'Dell, Ryan Andrew; Sun, Liangfeng

    2014-01-01

    Ultrasmall colloidal lead sulfide quantum dots can increase the open circuit voltages of quantum-dot-based solar cells because of their large energy gap. Their small size and visible or near infrared light-emitting property make them attractive to the applications of biological fluorescence labeling. Through a modified organometallic route, we can synthesize lead sulfide quantum dots as small as 1.6 nm in diameter. The low reaction temperature and the addition of a chloroalkane cosolvent decrease the reaction rate, making it possible to obtain the ultrasmall quantum dots. - Highlights: • Ultrasmall colloidal PbS quantum dots as small as 1.6 nm in diameter are synthesized. • The quantum dots emit red light with photoluminescence peak at 760 nm. • The growth temperature is as low as 50 °C. • Addition of cosolvent 1,2-dichloroethane in the reaction decreases the reaction rate

  2. Moving beyond mass-based parameters for conductivity analysis of sulfonated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yu Seung [Los Alamos National Laboratory; Pivovar, Bryan [NREL

    2009-01-01

    Proton conductivity of polymer electrolytes is critical for fuel cells and has therefore been studied in significant detail. The conductivity of sulfonated polymers has been linked to material characteristics in order to elucidate trends. Mass based measurements based on water uptake and ion exchange capacity are two of the most common material characteristics used to make comparisons between polymer electrolytes, but have significant limitations when correlated to proton conductivity. These limitations arise in part because different polymers can have significantly different densities and conduction happens over length scales more appropriately represented by volume measurements rather than mass. Herein, we establish and review volume related parameters that can be used to compare proton conductivity of different polymer electrolytes. Morphological effects on proton conductivity are also considered. Finally, the impact of these phenomena on designing next generation sulfonated polymers for polymer electrolyte membrane fuel cells is discussed.

  3. Patterning symmetry in the rational design of colloidal crystals

    Science.gov (United States)

    Romano, Flavio; Sciortino, Francesco

    2012-07-01

    Colloidal particles have the right size to form ordered structures with periodicities comparable to the wavelength of visible light. The tantalizing colours of precious opals and the colour of some species of birds are examples of polycrystalline colloidal structures found in nature. Driven by the demands of several emergent technologies, efforts have been made to develop efficient, self-assembly-based methodologies for generating colloidal single crystals with well-defined morphologies. Somewhat unfortunately, these efforts are often frustrated by the formation of structures lacking long-range order. Here we show that the rational design of patch shape and symmetry can drive patchy colloids to crystallize in a single, selected morphology by structurally eliminating undesired polymorphs. We provide a proof of this concept through the numerical investigation of triblock Janus colloids. One particular choice of patch symmetry yields, via spontaneous crystallization, a pure tetrastack lattice, a structure with attractive photonic properties, whereas another one results in a colloidal clathrate-like structure, in both cases without any interfering polymorphs.

  4. Luminescent Colloidal Semiconductor Nanocrystals Containing Copper: Synthesis, Photophysics, and Applications.

    Science.gov (United States)

    Knowles, Kathryn E; Hartstein, Kimberly H; Kilburn, Troy B; Marchioro, Arianna; Nelson, Heidi D; Whitham, Patrick J; Gamelin, Daniel R

    2016-09-28

    Copper-doped semiconductors are classic phosphor materials that have been used in a variety of applications for many decades. Colloidal copper-doped semiconductor nanocrystals have recently attracted a great deal of interest because they combine the solution processability and spectral tunability of colloidal nanocrystals with the unique photoluminescence properties of copper-doped semiconductor phosphors. Although ternary and quaternary semiconductors containing copper, such as CuInS2 and Cu2ZnSnS4, have been studied primarily in the context of their photovoltaic applications, when synthesized as colloidal nanocrystals, these materials have photoluminescence properties that are remarkably similar to those of copper-doped semiconductor nanocrystals. This review focuses on the luminescent properties of colloidal copper-doped, copper-based, and related copper-containing semiconductor nanocrystals. Fundamental investigations into the luminescence of copper-containing colloidal nanocrystals are reviewed in the context of the well-established luminescence mechanisms of bulk copper-doped semiconductors and copper(I) molecular coordination complexes. The use of colloidal copper-containing nanocrystals in applications that take advantage of their luminescent properties, such as bioimaging, solid-state lighting, and luminescent solar concentrators, is also discussed.

  5. Pore-Scale Mechanisms of Colloid Interfacial Retention as Studied With Confocal Microscopy

    Science.gov (United States)

    Lazouskaya, V.; Jin, Y.

    2006-12-01

    Due to environmental concerns related to migration of colloids and colloid-facilitated transport of contaminants, interfacial retention of colloids has drawn significant scientific attention in past years. Nevertheless, there are still questions that remain debatable or unanswered concerning the mechanisms of interfacial retention of colloids. The experimental tools traditionally include column experiments, which provide macroscopic experimental data, but not always ensure their non-ambiguous explanation. Pore-scale visualization techniques provide additional information on the occurring processes and serve the purpose of explaining the phenomena observed at larger scales. The progress in the field of microscopy provides state-of-the-art techniques for visualization experiments where behavior of single colloids can be observed and therefore analysis of the particular retention mechanism can be performed. We applied confocal microscopy to investigate the two most arguable sites of colloidal retention: AWI (air-water interface) and contact line, which proved itself as a promising technique. The benefits of confocal microscopy include visualization of single colloids, flexible positioning of the sample and therefore direct observation of the point of interest. In addition, fast image acquisition allows imaging experiments to be conducted under dynamic conditions. The combination of confocal imaging with the specialized imaging software provides the added advantage of quantitative evaluations of the acquired images. In our experiments, confocal microscopy was applied to investigate the retention of colloids on AWI and contact line as affected by colloid and solution properties (e.g., surface tension and ionic strength). Particular attention was given to the behavior of colloids on the contact line both in static and dynamic regimes including the investigation of moving evaporative fronts. Additionally, the importance of hydrodynamic effect on the colloidal retention at

  6. Colloid mobilization and arsenite transport in soil columns: effect of ionic strength.

    Science.gov (United States)

    Zhang, Hua; Selim, H M

    2007-01-01

    Colloid generation and transport in soils is of significance because of suspected colloid-facilitated transport of contaminants to the groundwater. In this study, colloid mobilization and its effect on the transport of arsenite [As(III)] were investigated in Olivier (fine-silty, mixed, active, thermic Aquic Fraglossudalfs) and Windsor (mixed, mesic typic Udipsamments) soil columns. Input solution of 10 mg L(-1) As(III) in 0.01 M NaCl was applied to water-saturated columns, and followed by leaching with deionized water (DIW). Flow interruptions were performed during the As(III) input and DIW leaching phases. Turbidity, electrical conductivity (EC), and pH of column effluents were monitored with time. Total and dissolved concentrations of As, Fe, and Al were analyzed. Effluent results demonstrated that colloid-facilitated transport contributed little to arsenic movement when the solution ionic strength was maintained constant. Mobilization of colloidal amorphous material and enhanced transport of As(III) were observed as a result of changes in ionic strength of the input solution. The peak of colloid generation coincided with peak concentrations of Fe, suggesting mobilization of Fe oxides and facilitated transport of As(III) adsorbed on oxide surfaces. Colloid mobilization was enhanced due to flow interruption in the Olivier column, which suggests slow dissociation of aggregated colloidal particles. Moreover, effluent results indicate significant effect of organic matter in stabilizing aggregates of colloidal particles.

  7. New operational modes for the Ta2O5-based electrolyte conductance cell

    NARCIS (Netherlands)

    Olthuis, Wouter; Smith, A.; van der Zalm, R.A.J.; Bergveld, Piet

    1994-01-01

    Based on the recently presented conductance cell, two specific operational modes are proposed. In the oscillator mode, the conductivity of the electrolyte determines the frequency of an oscillator, experimentally obtaining a shift from 10 to 27 kHz for a KCl concentration range from 0.5 to 100 mM.

  8. Characterization of colloids in groundwater

    International Nuclear Information System (INIS)

    Kim, J.I.; Buckau, G.; Klenze, R.

    1987-07-01

    Natural colloids in the Gorleben aquifer systems have been investigated as for their chemical composition, quantification and size distribution. Humic substances appear to be the major organic materials in these groundwaters, generating humic colloids which are analysed to be humic acid (and fulvic acid) loaded with a large number of trace heavy metal ions. These metal ions include natural homologues of actinides and some fission products in trivalent, tetravalent and hexavalent state. Concentrations of trivalent and tetravalent heavy metal ions are linearly correlated with the dissolved organic carbon (DDC) concentration in different groundwaters. The DOC is found to be present as humic colloids. The Am 3+ ions introduced in such a groundwater readily undergo the generation of its pseudocolloids through sorption or ion exchange reactions with humic colloids. The chemical behaviour of Am(III), being similar to the trivalent metal ions, e.g. Fe 3+ , REE etc. found in natural colloids, has been investigated by laser induced photoacoustic spectroscopy (LPAS). Groundwaters from Ispra, Markham Clinton and Felslabor Grimsel. Bidistilled water and one of Gorleben groundwaters, Gohy 1011, are taken for the purpose of comparison. This groundwater contains the least amount of natural colloids of all Gorleben groundwaters hitherto investigated. An indirect quantification is made by comparison of the LPAS results with experiment from Latex solution. (orig./IRB)

  9. STAR-POLYMER -- COLLOID MIXTURES

    Directory of Open Access Journals (Sweden)

    J.Dzubiella

    2002-01-01

    Full Text Available Recent results in theory and simulation of star-polymer--colloid mixtures are reviewed. We present the effective interaction between hard, colloidal particles and star polymers in a good solvent derived by monomer-resolved Molecular Dynamics simulations and theoretical arguments. The relevant parameters are the size ratio q between the stars and the colloids, as well as the number of polymeric arms f (functionality attached to the common center of the star. By covering a wide range of q's ranging from zero (star against a flat wall up to about 0.5, we establish analytical forms for the star-colloid interaction which are in excellent agreement with simulation results. By employing this cross interaction and the effective interactions between stars and colloids themselves, a demixing transition in the fluid phase is observed and systematically investigated for different arm numbers and size ratios. The demixing binodals are compared with experimental observations and found to be consistent. Furthermore, we map the full two-component system on an effective one-component description for the colloids, by inverting the two-component Ornstein-Zernike equations. Some recent results for the depletion interaction and freezing transitions are shown.

  10. Stratification in Drying Polymer-Polymer and Colloid-Polymer Mixtures.

    Science.gov (United States)

    Howard, Michael P; Nikoubashman, Arash; Panagiotopoulos, Athanassios Z

    2017-10-24

    Drying polymer-polymer and colloid-polymer mixtures were studied using Langevin dynamics computer simulations. Polymer-polymer mixtures vertically stratified into layers, with the shorter polymers enriched near the drying interface and the longer polymers pushed down toward the substrate. Colloid-polymer mixtures stratified into a polymer-on-top structure when the polymer radius of gyration was comparable to or smaller than the colloid diameter, and a colloid-on-top structure otherwise. We also developed a theoretical model for the drying mixtures based on dynamical density functional theory, which gave excellent quantitative agreement with the simulations for the polymer-polymer mixtures and qualitatively predicted the observed polymer-on-top or colloid-on-top structures for the colloid-polymer mixtures.

  11. A Field-Based Aquatic Life Benchmark for Conductivity in Central Appalachian Streams (Final Report)

    Science.gov (United States)

    EPA announced the availability of the final report, A Field-Based Aquatic Life Benchmark for Conductivity in Central Appalachian Streams. This report describes a method to characterize the relationship between the extirpation (the effective extinction) of invertebrate g...

  12. Measurement and Estimation of Effective Thermal Conductivity for Sodium based Nanofluid using 3-Omega Method

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Sun Ryung; Park, Hyun Sun [POSTECH, Pohang (Korea, Republic of); Kim, Moo Hwan [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    The sodium-cooled fast reactor (SFR) is one of generation IV type reactors and has been extensively researched since 1950s. A strong advantage of the SFR is its liquid sodium coolant which is well-known for its superior thermal properties. However, in terms of possible pipe leakage or rupture, a liquid sodium coolant possesses a critical issue due to its high chemical reactivity which leads to fire or explosion. Due to its safety concerns, dispersion of nanoparticles in liquid sodium has been proposed to reduce the chemical reactivity of sodium. In case of sodium based titanium nanofluid (NaTiNF), the chemical reactivity suppression effect when interacting with water has been proved both experimentally and theoretically [1,2]. Suppression of chemical reactivity is critical without much loss of high heat transfer characteristic of sodium. As there is no research conducted for applying 3-omega sensor in liquid metal as well as high temperature liquid, the sensor development is performed for using in NaTiNF as well as effective thermal conductivity model validation. Based on the acquired effective thermal conductivity of NaTiNF, existing effective thermal conductivity models are evaluated. Thermal conductivity measurement is performed for liquid sodium based titanium nanofluid (NaTiNF) through 3-Omega method. The experiment is conducted at three temperature points of 120, 150, and 180 .deg. C for both pure liquid sodium and NaTiNF. By using 3- omega sensor, thermal conductivity measurement of liquid metal can be more conveniently conducted in labscale. Also, its possibility to measure the thermal conductivity of high temperature liquid metal with metallic nanoparticles being dispersed is shown. Unlike other water or oil-based nanofluids, NaTiNF exhibits reduction of thermal conductivity compare with liquid sodium. Various nanofluid models are plotted, and it is concluded that the MSBM which considers interfacial resistance and Brownian motion can be used in predicting

  13. Measurement and Estimation of Effective Thermal Conductivity for Sodium based Nanofluid using 3-Omega Method

    International Nuclear Information System (INIS)

    Oh, Sun Ryung; Park, Hyun Sun; Kim, Moo Hwan

    2016-01-01

    The sodium-cooled fast reactor (SFR) is one of generation IV type reactors and has been extensively researched since 1950s. A strong advantage of the SFR is its liquid sodium coolant which is well-known for its superior thermal properties. However, in terms of possible pipe leakage or rupture, a liquid sodium coolant possesses a critical issue due to its high chemical reactivity which leads to fire or explosion. Due to its safety concerns, dispersion of nanoparticles in liquid sodium has been proposed to reduce the chemical reactivity of sodium. In case of sodium based titanium nanofluid (NaTiNF), the chemical reactivity suppression effect when interacting with water has been proved both experimentally and theoretically [1,2]. Suppression of chemical reactivity is critical without much loss of high heat transfer characteristic of sodium. As there is no research conducted for applying 3-omega sensor in liquid metal as well as high temperature liquid, the sensor development is performed for using in NaTiNF as well as effective thermal conductivity model validation. Based on the acquired effective thermal conductivity of NaTiNF, existing effective thermal conductivity models are evaluated. Thermal conductivity measurement is performed for liquid sodium based titanium nanofluid (NaTiNF) through 3-Omega method. The experiment is conducted at three temperature points of 120, 150, and 180 .deg. C for both pure liquid sodium and NaTiNF. By using 3- omega sensor, thermal conductivity measurement of liquid metal can be more conveniently conducted in labscale. Also, its possibility to measure the thermal conductivity of high temperature liquid metal with metallic nanoparticles being dispersed is shown. Unlike other water or oil-based nanofluids, NaTiNF exhibits reduction of thermal conductivity compare with liquid sodium. Various nanofluid models are plotted, and it is concluded that the MSBM which considers interfacial resistance and Brownian motion can be used in predicting

  14. Colloid remediation in groundwater by polyelectrolyte capture

    International Nuclear Information System (INIS)

    Nuttall, H.E.; Rao, S.; Jain, R.

    1992-01-01

    This paper describes an ongoing study to characterize groundwater colloids, to understand the geochemical factors affecting colloid transport in groundwater, and to develop an in-situ colloid remediation process. The colloids and suspended particulate matter used in this study were collected from a perched aquifer site that has radiation levels several hundred times the natural background and where previous researchers have measured and reported the presence of radiocolloids containing plutonium and americium. At this site, radionuclides have spread over several kilometers. Inorganic colloids collected from water samples are characterized with respect to concentration, mineralogy, size distribution, electrophoretic mobility (zeta potential), and radioactivity levels. Presented are the methods used to investigate the physiochemical factors affecting colloid transport and the preliminary analytical results. Included below are a description of a colloid transport model and the corresponding computational code, water analyses, characterization of the inorganic colloids, and a conceptual description of a process for in-situ colloid remediation using the phenomenon of polyelectrolyte capture

  15. Investigation on the Electrical Conductivity of Transformer Oil-Based AlN Nanofluid

    Directory of Open Access Journals (Sweden)

    M. Dong

    2013-01-01

    Full Text Available Aluminum-nitride-(AlN-transformer oil-based nanofluid was prepared by dispersing AlN nanoparticles in transformer oil. The composition-dependent electrical conductivity of AlN-transformer oil nanofluid was investigated at different ambient temperatures. The results indicate the nonlinear dependences of the electrical conductivity on volumetric fraction and temperature. In comparison to the pure transformer oil, the electrical conductivity of nanofluid containing 0.5% AlN nanoparticles has increased by 1057 times at 60°C. By considering the electrophoresis of the AlN nanoparticles, a straightforward electrical conductivity model is established to modulate and understand the experiment results.

  16. Conductance of graphene based normal-superconductor junction with double magnetic barriers

    Science.gov (United States)

    Abdollahipour, B.; Mohebalipour, A.; Maleki, M. A.

    2018-05-01

    We study conductance of a graphene based normal metal-superconductor junction with two magnetic barriers. The magnetic barriers are induced via two applied magnetic fields with the same magnitudes and opposite directions accompanied by an applied electrostatic potential. We solve Dirac-Bogoliubov-De-Gennes (DBdG) equation to calculate conductance of the junction. We find that applying the magnetic field leads to suppression of the Andreev reflection and conductance for all energies. On the other hand, we observe a crossover from oscillatory to tunneling behavior of the conductance as a function of the applied potential by increasing the magnetic field.

  17. Conductivity of SrTiO3 based oxides in the reducing atmosphere at high temperature

    DEFF Research Database (Denmark)

    Hashimoto, Shin-Ichi; Poulsen, Finn Willy; Mogensen, Mogens Bjerg

    2007-01-01

    The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... at 500-800 degrees C, while that of La-doped SrTiO3 dropped immediately on exposure to air. The conduction behavior of Nb-doped SrTiO3 was explained by reduction of Ti4+ and/or Nb5+ and the relatively slow oxygen diffusibility. (c) 2006 Elsevier B.V. All rights reserved.......The conductivities of several donor-doped SrTiO3 based oxides, which were prepared in air, were studied in a reducing atmosphere at high temperature. The conductivities of all specimens increased slowly with time at 1000 degrees C in 9% H-2/N-2, even after 100 h. Nb-doped SrTiO3 showed relatively...... fast reduction and high conductivity compared with the other SrTiO3 based oxides. The conductivity of Nb-doped SrTiO3 was ca. 50 S cm(-1) at 500 degrees C after reduction at 1200 degrees C. After strong reduction, the conductivity of Nb-doped SrTiO3 was almost independent of the oxygen partial pressure...

  18. Evaluation of colloid transport issues and recommendations for SKI performance assessments

    International Nuclear Information System (INIS)

    Wickham, S. M.; Bennett, D. G.; Higgo, J. J. W.

    2000-08-01

    The primary objective of this project was to develop recommendations to SKI for evaluating the potential significance of colloids in performance assessment (PA) studies by: Updating a previous review of the treatment of colloids in PA studies for radioactive waste repositories and to include information on PAs published in the period 1997-1999. We have reviewed sixteen PAs conducted in nine countries and have made the following observations: All PAs include colloid formation and colloid transport in their FEP list. Although some programmes have deferred consideration of colloidal radionuclide transport until further research has been performed, more recent PAs do account for the effects of colloids. PAs of disposal systems in which the waste canister is surrounded by a bentonite buffer do not consider the effect of colloids on the source term. These PAs assume that all colloids are filtered by the bentonite buffer and cannot escape from the near-field. PAs of disposal systems with no bentonite buffer have to account for mobilisation of radionuclides from the waste by colloids. The concentration of colloids that may form in the repository is a key uncertainty. Many PA programmes have modelled colloidal radionuclide transport in the geosphere using one-dimensional transport equations. No PA has included a comprehensive treatment of colloid transport using mechanistic modelling. Some PAs have not undertaken modelling of colloid transport in the geosphere, but have relied instead on arguments that such transport processes will be of low consequence to the performance of the disposal system. Five PAs have shown the effects of colloid transport through the geosphere to be potentially significant. For the disposal of spent nuclear fuel, SKB has developed the KBS-3 concept. For the disposal of long-lived low-level and intermediate-level radioactive waste, SKB has developed the SFL 3-5 concept. In the SFL 3-5 concept, waste is placed in underground disposal caverns and

  19. Three-dimensional graphene foam-based transparent conductive electrodes in GaN-based blue light-emitting diodes

    Science.gov (United States)

    Kim, Byung-Jae; Yang, Gwangseok; Joo Park, Min; Seop Kwak, Joon; Hyeon Baik, Kwang; Kim, Donghwan; Kim, Jihyun

    2013-04-01

    We demonstrated three-dimensional (3D) graphene foam-based transparent conductive electrodes in GaN-based blue light-emitting diodes (LEDs). A 3D graphene foam structure grown on 3D Cu foam using a chemical vapor deposition method was transferred onto a p-GaN layer of blue LEDs. Optical and electrical performances were greatly enhanced by employing 3D graphene foam as transparent conductive electrodes in blue LED devices, which were analyzed by electroluminescence measurements, micro-Raman spectroscopy, and light intensity-current-voltage testing. The forward operating voltage and the light output power at an injection current of 100 mA of the GaN-based blue LEDs with a graphene foam-based transparent conductive electrode were improved by ˜26% and ˜14%, respectively. The robustness, high transmittance, and outstanding conductivity of 3D graphene foam show great potentials for advanced transparent conductive electrodes in optoelectronic devices.

  20. Latino Community-Based Participatory Research Studies: A Model for Conducting Bilingual Translations

    Science.gov (United States)

    Sánchez-Johnsen, Lisa; Escamilla, Julia; Rodriguez, Erin M.; Vega, Susan; Bolaños, Liliana

    2015-01-01

    Many behavioral health materials have not been translated into Spanish. Of those that are available in Spanish, some of them have not been translated correctly, many are only appropriate for a subgroup of Latinos, and/or multiple versions of the same materials exist. This article describes an innovative model of conducting bilingual English–Spanish translations as part of community-based participatory research studies and provides recommendations based on this model. In this article, the traditional process of conducting bilingual translations is reviewed, and an innovative model for conducting translations in collaboration with community partners is described. Finally, recommendations for conducting future health research studies with community partners are provided. Researchers, health care providers, educators, and community partners will benefit from learning about this innovative model that helps produce materials that are more culturally appropriate than those that are produced with the most commonly used method of conducting translations. PMID:25741929

  1. Electrical conductance change of graphene-based devices upon surface modification for detecting botulinum neurotoxin

    Science.gov (United States)

    Kim, Daehee; Kim, Ho-Jong; Shim, Seung-Bo; Jung, Suyong; Lee, Nam Hee; Nahm, Seung Hoon; Shin, Eui-Cheol; Yun, Wan Soo; Ha, Dong Han

    2017-06-01

    We report an electric conductance change in a graphene-based device upon molecular adsorption for detecting botulinum neurotoxin (BoNT) using the antibody-antigen binding strategy. This device consists of a 400-µm-wide monolayer of graphene between the source and drain electrodes. As-fabricated devices exhibit p-type behaviors. After modifying graphene with linkers and antibodies, BoNT detection was performed by dropping a target solution and measuring the conductance change of the devices. The immobilization of linkers on graphene decreases the electrical conductance as a result of electron transfer from linkers to graphene. However, the conductance change caused by the adsorption of antibodies or BoNTs is ascribed to the top-gating effects of the molecules adsorbed on graphene. The normalized conductance change of the graphene-based device upon antibody-BoNT binding was greater than 5%.

  2. Graphite nanoplatelets and carbon nanotubes based polyethylene composites: Electrical conductivity and morphology

    International Nuclear Information System (INIS)

    Haznedar, Galip; Cravanzola, Sara; Zanetti, Marco; Scarano, Domenica; Zecchina, Adriano; Cesano, Federico

    2013-01-01

    Graphite nanoplatelets (GNPs) and/or multiwalled-carbon nanotubes (MWCNTs)/low density polyethylene (LDPE) composites have been obtained either via melt-mixing or solvent assisted methods. Electrical properties of samples obtained through the above mentioned methods are compared and the conductance values as function of filler fraction are discussed. The corresponding percolation thresholds are evaluated. Conductivity maps images are acquired under low-potentials scanning electron microscopy (0.3 KV) and the relationship between the obtained conductivity images and electric properties is highlighted. The synergistic role of CNTs (1D) and GNPs (2D) in improving the conductive properties of the polymer composites has been shown. - Highlights: • Graphite nanoplatelets (GNPs) and GNPs/MWCNT LDPE composites. • Low potential SEM conductivity maps. • Conducting paths between 1D and 2D C-structures (synergistic effect) are obtained. • Composites based on hybrid 1D/2D combinations show lower percolation thresholds

  3. Colloid facilitated transport of lanthanides through discrete fractures in chalk

    Science.gov (United States)

    Tran, Emily; Klein Ben-David, Ofra; Teutsch, Nadya; Weisbrod, Noam

    2015-04-01

    transport rates and calculation of overall tracer recovery. Preliminary results suggest that mobility of Ce as a solute is negligible, and in experiments conducted without bentonite colloids, the 2% of the Ce that was recovered during the experiments travelled as "intrinsic" colloids in the form of Ce2(CO3)3-6H2O precipitate. However, the total recovery of the Ce increased to 9% when it was injected into the core in the presence of bentonite colloids and 13% when both bentonite and the carbonate precipitate colloids were injected. In addition, the maximum relative concentration (C/C0) of the Ce in the samples from the experiments conducted without bentonite colloids is about 0.002, whereas that of the experiments conducted in the presence of bentonite colloids reaches almost 0.2. This indicates that colloid presence does indeed markedly increase the mobility of radionuclides through fractured chalk matrices and should therefore be considered in models representing transport of radionuclide waste originating from nuclear repositories.

  4. Microgels: Novel Colloidal Materials

    Directory of Open Access Journals (Sweden)

    Fernández-Nieves, A.

    2000-08-01

    Full Text Available Microgels are novel colloidal gels widely used because of the swelling or de-swelling exhibited under specific external conditions. In this work, the swelling and de-swelling of microgel particles is experimentally described. The medium pH, salt concentration and osmotic stress, are the three variables with which the change of phase has been realised. All transitions are found to occur well above the critical point of the system. Additionally, the basic applications in which the given transition is employed are described.

    Los microgeles son geles coloidales que se emplean por el inflado y/o desinflado que manifiestan ante ciertas condiciones externas. En este trabajo, se describe experimentalmente el inflado y el desinflado de partículas de gel. El pH del medio, su concentración iónica y el esfuerzo osmótico externo son las variables externas que se emplean para provocar el cambio de fase en las partículas. Todas las transiciones ocurren por encima del punto crítico del sistema. Adicionalmente, se presentan algunas de las aplicaciones en donde se emplea la transición provocada por la variable externa concreta.

  5. Enhanced Transport of Colloid And Metal Cations by Freeze-thaw Cycles

    Science.gov (United States)

    Mohanty, S. K.; Ryan, J. N.; Saiers, J. E.; Laboratory experiment

    2011-12-01

    Understanding the mechanisms of colloid mobilization is essential to predicting the importance of colloid-facilitated transport of contaminants in subsurface environments. This study was conducted to evaluate the effect of freeze-thaw cycles on the mobilization of colloids and colloid-facilitated transport of cesium and strontium in intact soil cores. The soil cores were collected from a watershed in Tennessee, USA, where the soils are weathered from limey shale with fractured saprolite subsoils that have illite as the primary clay mineral. Each freeze-thaw cycle involved freezing the contaminated soil at -15 °C for 36 h followed by thawing at 25 °C for 24 h and infiltration of rainwater for 6 h. An 18-port grid was used to collect water sample from preferential flow paths. The amount of colloids mobilized by the freeze-thaw process was compared with the amount of colloids mobilized from a control soil-core at room temperature. The colloids mobilized during freeze-thaw were characterized using x-ray diffraction analysis. Results of current study indicated an enhanced mobilization of colloids from frozen soil compared to unfrozen soil. Colloids mobilized after five freeze-thaw cycles were two times higher than the amount of colloids mobilized from unfrozen soil. The duration of freezing had no significant impact on the amount of colloids mobilized. Results of XRD analysis indicated an increase in clay mineral and iron-containing minerals and a decrease in quartz fractions in the mobilized colloids compared to the soil from which colloids were mobilized. The soil consisted of 35.7% clay minerals, 43.3% quartz, and 1.5% iron-containing minerals including ferruginous smectite, goethite, and amphibole. In contrast, colloids mobilized from the soil by freeze-thaw cycles had 64.3% clay minerals, 21.7% quartz, and 5.5% of iron-containing minerals. The colloids mobilized in control soil had 73.7% clay minerals, 3.5% quartz, and 4.6% iron-containing minerals. The colloidal

  6. The thermal conductivity of clustered nanocolloids

    Directory of Open Access Journals (Sweden)

    Saba Lotfizadeh

    2014-06-01

    Full Text Available We quantify the effect of clustering on the thermal conductivity of colloidal dispersions using silane-treated silica, a system engineered to exhibit reversible clustering under well-controlled conditions. We show that the thermal conductivity increases monotonically with cluster size and spans the entire range between the two limits of Maxwell's theory. The results, corroborated by numerical simulation, demonstrate that large increases of the thermal conductivity of colloidal dispersions are possible, yet fully within the predictions of classical theory.

  7. Colloid-Facilitated Transport of Plutonium, Pu(+V), in Saturated Alluvium

    Science.gov (United States)

    Abdel-Fattah, A. I.; Reimus, P. W.; Ware, S.; Haga, M. H.

    2004-12-01

    Natural groundwater colloids can facilitate the subsurface transport of strongly-sorbing radionuclides, such as plutonium (Pu). To evaluate this mechanism, packed-bed column experiments were conducted, comparing the simultaneous transport of dissolved plutonium (Pu-239) of an initial oxidation state (+V), Pu sorbed onto natural colloids, 190-nm and 500-nm diameter fluorescent Carboxylate Modified Latex (CML) microspheres, and tritium, as a conservative tracer, in saturated alluvium. The experiments were conducted in two columns having slightly different porosities at two flow rates, resulting in average linear velocities, v, of 0.6 to 3.65 cm/hr in one column and 0.57 to 2.85 cm/hr in the other. In all experiments, Pu associated with natural colloids transported through alluvium essentially unretarded, while dissolved Pu was entirely retained. These results were consistent with the strong sorption of Pu to alluvium and the negligible desorption from natural colloids, observed in separate batch experiments, over time scales exceeding those of the column experiments. The breakthrough of natural colloids preceded that of tritium in all experiments, indicating a slightly smaller effective pore volume for the colloids. The enhancement of colloids' transport over tritium decreased with v, implying ~40% enhancement at v = 0. The 500-nm CML microspheres were significantly attenuated in the column experiments compared to the 190-nm microspheres, which exhibited slightly more attenuation than natural colloids.

  8. Colloid-facilitated Transport of Phosphorus In A Coarse Sandy Loam: Variations At Field Scale

    Science.gov (United States)

    de Jonge, L. W.; Schelde, K.; Rubaek, G. H.; Moldrup, P.

    Strongly sorbing compounds such as phosphorus, pesticides, and heavy metals can be transported through the soil adsorbed to mobile colloidal particles. The aim of this work was to study the spatial variation in colloid-facilitated transport of phosphorus at field scale. Irrigation experiments were carried out in the laboratory on forty-two 20 cm times 20 cm undisturbed soil columns sampled in a grid covering 25 m times 30 m of an agricultural field. The experiments exhibited a great variation among the columns in the accumulated mass of particles and phosphorus leached during the 2.5 hrs of irrigation. The columns with the highest mass of leached particles were located at a specific part of the agricultural field. The mass of particles was negatively correlated to the average electrical conductivity of the effluent and positively correlated to the macropore velocity. The accumulated mass of leached particular organic and inorganic phosphorus was linearly related to the accumulated mass of leached particles. A pore connectivity index based on measured soil-air permeability an macro-porosity was used as part of a predictor for colloidal transport.

  9. Migration of uranium in the presence of clay colloids in a sandy aquifer

    International Nuclear Information System (INIS)

    Le Cointe, P.; Grambow, B.; Piscitelli, A.; Montavon, G.; Van der Lee, J.; Giffaut, E.; Schneider, V.

    2010-01-01

    polystyrene standards on different sediment samples (core sample, reconsolidated auger sample and clay-free reconsolidated auger sample). The filtration threshold has been defined between 70 and 100 nm, except for the clay-free sample, for which it is above 500 nm. Laboratory column experiments were performed with 70 nm clay colloids, U(VI) and clay colloids + U(VI). To make the system simpler, the clay fraction was removed from the sediment and the experiments were carried out at a low ionic strength, to avoid clay colloids flocculation. The breakthrough behaviour of clay colloids and U(VI) was monitored and compared to conservative tracers (HTO and 36 Cl). The data were modelled with the HYTEC reactive transport code developed at the Paris School of Mines, considering both hydrodynamic properties of the porous system (porosity of 30%, Darcy velocity fixed to 3.10 -6 m/s, close to the one measured in situ) and the parameters quantifying U(VI)-Quartz and U(VI)-Clay interactions. An in situ tracing experiment was also conducted with both conservative (D 2 O, H 2 18 O) and colloidal (polystyrene nanoparticles) tracers. The objective is to ensure the reactive transport model, based on laboratory experiments, can be extended to a parcel of the site, and finally to the whole site, using experimental and modelling data collected by Andra. (authors)

  10. The chemical and colloidal stability of polyaniline dispersions

    Czech Academy of Sciences Publication Activity Database

    Blinova, Natalia V.; Sapurina, I.; Klimovič, J.; Stejskal, Jaroslav

    2005-01-01

    Roč. 88, č. 3 (2005), s. 428-434 ISSN 0141-3910 R&D Projects: GA AV ČR(CZ) IAA4050313; GA MŠk(CZ) ME 539 Institutional research plan: CEZ:AV0Z40500505 Keywords : polyaniline * conducting polymer * colloids Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.749, year: 2005

  11. Development of a model colloidal system for rheology simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Schunk, Peter Randall; Tallant, David Robert; Piech, Martin (United Technologies Research Center, East Hartford, CT); Bell, Nelson Simmons; Frischknecht, Amalie Lucile

    2008-10-01

    The objective of the experimental effort is to provide a model particle system that will enable modeling of the macroscopic rheology from the interfacial and environmental structure of the particles and solvent or melt as functions of applied shear and volume fraction of the solid particles. This chapter describes the choice of the model particle system, methods for synthesis and characterization, and results from characterization of colloidal dispersion, particle film formation, and the shear and oscillatory rheology in the system. Surface characterization of the grafted PDMS interface, dispersion characterization of the colloids, and rheological characterization of the dispersions as a function of volume fraction were conducted.

  12. Nonequilibrium Equation of State in Suspensions of Active Colloids

    Directory of Open Access Journals (Sweden)

    Félix Ginot

    2015-01-01

    Full Text Available Active colloids constitute a novel class of materials composed of colloidal-scale particles locally converting chemical energy into motility, mimicking micro-organisms. Evolving far from equilibrium, these systems display structural organizations and dynamical properties distinct from thermalized colloidal assemblies. Harvesting the potential of this new class of systems requires the development of a conceptual framework to describe these intrinsically nonequilibrium systems. We use sedimentation experiments to probe the nonequilibrium equation of state of a bidimensional assembly of active Janus microspheres and conduct computer simulations of a model of self-propelled hard disks. Self-propulsion profoundly affects the equation of state, but these changes can be rationalized using equilibrium concepts. We show that active colloids behave, in the dilute limit, as an ideal gas with an activity-dependent effective temperature. At finite density, increasing the activity is similar to increasing adhesion between equilibrium particles. We quantify this effective adhesion and obtain a unique scaling law relating activity and effective adhesion in both experiments and simulations. Our results provide a new and efficient way to understand the emergence of novel phases of matter in active colloidal suspensions.

  13. Colloidal polyaniline dispersions: antibacterial activity, cytotoxicity and neutrophil oxidative burst.

    Science.gov (United States)

    Kucekova, Zdenka; Humpolicek, Petr; Kasparkova, Vera; Perecko, Tomas; Lehocký, Marián; Hauerlandová, Iva; Sáha, Petr; Stejskal, Jaroslav

    2014-04-01

    Polyaniline colloids rank among promising application forms of this conducting polymer. Cytotoxicity, antibacterial activity, and neutrophil oxidative burst tests were performed on cells treated with colloidal polyaniline dispersions. The antibacterial effect of colloidal polyaniline against gram-positive and gram-negative bacteria was most pronounced for Bacillus cereus and Escherichia coli, with a minimum inhibitory concentration of 3,500 μg mL(-1). The data recorded on human keratinocyte (HaCaT) and a mouse embryonic fibroblast (NIH/3T3) cell lines using an MTT assay and flow cytometry indicated a concentration-dependent cytotoxicity of colloid, with the absence of cytotoxic effect at around 150 μg mL(-1). The neutrophil oxidative burst test then showed that colloidal polyaniline, in concentrations <150 μg mL(-1), was not able to stimulate the production of reactive oxygen species in neutrophils and whole human blood. However, it worked efficiently as a scavenger of those already formed. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Empirically Supported Family-Based Treatments for Conduct Disorder and Delinquency in Adolescents

    Science.gov (United States)

    Henggeler, Scott W.; Sheidow, Ashli J.

    2012-01-01

    Several family-based treatments of conduct disorder and delinquency in adolescents have emerged as evidence-based and, in recent years, have been transported to more than 800 community practice settings. These models include multisystemic therapy, functional family therapy, multidimensional treatment foster care, and, to a lesser extent, brief…

  15. Conducting Task-Based Interviews with Pairs of Children: Consensus, Conflict, Knowledge Construction and Turn Taking

    Science.gov (United States)

    Houssart, Jenny; Evens, Hilary

    2011-01-01

    This article explores theoretical and methodological issues associated with task-based interviews conducted with pairs of children. We explore different approaches to interviews from sociological, psychological and subject-based perspectives. Our interviews, concerning mathematical questions and carried out with pairs of 10 and 11-year-olds, are…

  16. The radiation chemistry of colloids

    International Nuclear Information System (INIS)

    Sellers, R.M.

    1976-08-01

    One of the most important problems associated with water cooled reactors is the accumulation on the pipework of radio-active deposits. These are formed from corrosion products which become activated during their passage through the reactor core. The first step of the activation process involves the deposition of the corrosion products, which are present as either colloidal or particulate matter, onto surfaces in the reactor core, i.e. within the radiation zone. A review of the literature on the effect of radiation on colloids is presented. Particular emphasis is given to the dependence of colloidal parameters such as particle size, turbidity and electrophoretic mobility on radiation dose. Most of the data available is of a qualitative nature only. Evidence is presented that colloids of iron are affected (in some cases precipitated) by radiation, and it is suggested that this process plays a part in the deposition of corrosion products in nuclear reactor cores. The bulk of the information available can be rationalized in terms of the radiation chemistry of aqueous solutions, and the interaction of the radicals produced with the atoms or molecules at the surface of the colloidal particles. This approach is very successful in explaining the variation of the mean particle size of monodisperse sulphur hydrosols with dose, for which quantitative experimental data are available. (author)

  17. Nanopore surface coating delivers nanopore size and shape through conductance-based sizing.

    Science.gov (United States)

    Frament, Cameron M; Bandara, Nuwan; Dwyer, Jason R

    2013-10-09

    The performance of nanopore single-molecule sensing elements depends intimately on their physical dimensions and surface chemical properties. These factors underpin the dependence of the nanopore ionic conductance on electrolyte concentration, yet the measured, or modeled, dependence only partially illuminates the details of geometry and surface chemistry. Using the electrolyte-dependent conductance data before and after selective surface functionalization of solid-state nanopores, however, introduces more degrees of freedom and improves the performance of conductance-based nanopore characterizations. Sets of representative nanopore profiles were used to generate conductance data, and the nanopore shape and exact dimensions were identified, through conductance alone, by orders-of-magnitude reductions in the geometry optimization metrics. The optimization framework could similarly be used to evaluate the nanopore surface coating thickness.

  18. Research of a Novel Three-dimensional Force Flexible Tactile Sensor Based on Conductive Rubber

    Directory of Open Access Journals (Sweden)

    Fei Xu

    2010-09-01

    Full Text Available A novel three-dimensional force flexible tactile sensor using conductive rubber with "overall injection molding" technique is presented. The sensor is based on conductive rubber’s force-sensitive property. The sensor is flexible and can measure 3-D force. The rubber’s characteristics, the sensor’s structure and its principle are described. The results of simulation will be also presented.

  19. Synthesis of nonionic-anionic colloidal systems based on alkaline and ammonium β-nonylphenol polyethyleneoxy (n = 3-20) propionates/dodecylbenzenesulfonates with prospects for food hygiene.

    Science.gov (United States)

    Jianu, Calin

    2012-09-08

    The main objective of this work was to obtain a binary system of surface-active components (nonionic soap - alkaline and/or ammonium dodecylbenzenesulfonate) with potential competences in food hygiene, by accessing a scheme of classical reactions (cyanoethylation, total acid hydrolysis and stoichiometric neutralization with inorganic alkaline and/or organic ammonium bases) adapted to heterogeneously polyethoxylated nonylphenols (n = 3-20). In the processing system mentioned, dodecylbenzenesulfonic acid, initially the acid catalyst for the exhaustive hydrolysis of β-nonylphenolpolyethyleneoxy (n = 3-20) propionitriles, becomes together with the nonionic soap formed the second surface-active component of the binary system. In the reaction scheme adopted the influence of the main operating (duration, temperature, molar ratio of reagents) and structural parameters (degree of oligomerization of the polyoxyethylene chain) on the processing yields for the synthetic steps was followed. The favorable role of the polyoxyethylene chain size is remarked, through its specific conformation and its alkaline cations sequestration competences on the yields of cyanoethylation, but also the beneficial influence of phase-transfer catalysts in the total acid hydrolysis step. The chemical stability of dodecylbenzenesulfonic acid (DBSH) at the temperature and strongly acidic pH of the reaction environment is confirmed. The controlled change of the amount of DBSH in the final binary system will later confer it potential colloidal competences in food hygiene receipts. The preliminary synthetic tests performed confirmed the prospect of obtaining a broad range of useful colloidal competences in various food hygiene scenarios.

  20. The effect of functionalized silver nanoparticles over the thermal conductivity of base fluids

    Science.gov (United States)

    Seyhan, Merve; Altan, Cem Levent; Gurten, Berna; Bucak, Seyda

    2017-04-01

    Thermal conductivities of nanofluids are expected to be higher than common heat transfer fluids. The use of metal nanoparticles has not been intensely investigated for heat transfer applications due to lack of stability. Here we present an experimental study on the effect of silver nanoparticles (Ag NPs) which are stabilized with surfactants, on the thermal conductivity of water, ethylene glycol and hexane. Hydrophilic Ag NPs were synthesized in aqueous medium with using gum arabic as surfactant and oleic acid/oleylamine were used to stabilize Ag NPs in the organic phase. The enhancement up to 10 per cent in effective thermal conductivity of hexane and ethylene glycol was achieved with addition of Ag NPs at considerably low concentrations (i.e. 2 and 1 per cent, by weight, for hexane and ethylene glycol respectively). However, almost 10 per cent of deterioration was recorded at effective thermal conductivity of water when Ag NPs were added at 1 per cent (by wt). Considerable amount of Gum Arabic in the medium is shown to be the major contributor to this fall, causing lowering of thermal conductivity of water. Same particles performed much better in ethylene glycol where the stabilizer does not lower the thermal conductivity of the base fluid. Also thermal conductivity of nanofluids was found to be temperature independent except water based Ag nanofluids above a threshold concentration. This temperature dependency is suggested to be due to inhibition of hydrogen bonding among water molecules in the presence of high amounts of gum arabic.

  1. Adsorption of polar, nonpolar, and substituted aromatics to colloidal graphene oxide nanoparticles

    NARCIS (Netherlands)

    Wang, Fang; Haftka, Joris J H; Sinnige, Theo L.; Hermens, Joop L M; Chen, Wei

    2014-01-01

    We conducted batch adsorption experiments to understand the adsorptive properties of colloidal graphene oxide nanoparticles (GONPs) for a range of environmentally relevant aromatics and substituted aromatics, including model nonpolar compounds (pyrene, phenanthrene, naphthalene, and

  2. Colloid Thrusters, Physics, Fabrication and Performance

    National Research Council Canada - National Science Library

    Martinez-Sanchez, Manuel; Akinwande, Akintunde I

    2005-01-01

    ... discovered pure ionic mode, the microfabrication in Silicon of two types of arrays of colloid or electrospray emitters, and the development of a quantitative theory for the colloidal regime (no ions...

  3. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

    2015-08-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

  4. COLLOID RELEASE AND E. COLI TRANSPORT IN INTACT AGRICULTURAL SOIL COLUMNS

    Directory of Open Access Journals (Sweden)

    Sandip Patil

    2012-12-01

    Full Text Available During animal waste agricultural applications, the major concern is the pathogen spreading, which may contaminate groundwater. Colloid release and pathogen transport during irrigation were evaluated in intact agricultural soil columns in this research using Escherichia coli as a model strain. In order to be easily identified and quantified, E. coli was incorporated with green fluorescent protein genes. The experiments were conducted at a water flow rate of 100 ml/min and the elution was collected and analized for colloid release and E. coli transport. Colloid release and E. coli transport were simulated using an implicit, finite-difference scheme with colloid release rate coefficient and E. coli deposition rate coefficient as constant, linear and exponential functions of the soil depth, respectively. It seemed that exponential functions had the best fit against the colloid release and E. coli transport observations.

  5. COLLOID RELEASE AND E. COLI TRANSPORT IN INTACT AGRICULTURAL SOIL COLUMNS

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2012-01-01

    Full Text Available During animal waste agricultural applications, the major concern is the pathogen spreading, which may contaminate groundwater. Colloid release and pathogen transport during irrigation were evaluated in intact agricultural soil columns in this research using Escherichia coli as a model strain. In order to be easily identified and quantified, E. coli was incorporated with green fluorescent protein genes. The experiments were conducted at a water flow rate of 100 ml/min and the elution was collected and analized for colloid release and E. coli transport. Colloid release and E. coli transport were simulated using an implicit, finite-difference scheme with colloid release rate coefficient and E. coli deposition rate coefficient as constant, linear and exponential functions of the soil depth, respectively. It seemed that exponential functions had the best fit against the colloid release and E. coli transport observations.

  6. Colloid release from soil aggregates

    DEFF Research Database (Denmark)

    Vendelboe, Anders Lindblad; Møldrup, Per; Schjønning, Per

    2012-01-01

    The content of water-dispersible colloids (WDC) has a major impact on soil functions and structural stability. In addition, the presence of mobile colloids may increase the risk of colloid-facilitated transport of strongly sorbing environmental contaminants. The WDC content was measured in 39 soils......, using laser diffraction, by agitating the samples using a wet-dispersion unit. This approach eliminated the need for long sedimentation times required by the more classical end-over-end shaking approach and provided information about the time-dependent release of WDC. The total clay content of the soils...... ranged from 0.1 to 0.44 kg kg−1. The WDC content was measured on air-dry and moist 1- to 2-mm aggregates. The WDC content at a reference time was highly correlated to the total clay content (r > 0.91, P soils. Only for two sites was the WDC content correlated to the content of clay...

  7. Colloidal transport by active filaments.

    Science.gov (United States)

    Manna, Raj Kumar; Kumar, P B Sunil; Adhikari, R

    2017-01-14

    Enhanced colloidal transport beyond the limit imposed by diffusion is usually achieved through external fields. Here, we demonstrate the ballistic transport of a colloidal sphere using internal sources of energy provided by an attached active filament. The latter is modeled as a chain of chemo-mechanically active beads connected by potentials that enforce semi-flexibility and self-avoidance. The fluid flow produced by the active beads and the forces they mediate are explicitly taken into account in the overdamped equations of motion describing the colloid-filament assembly. The speed and efficiency of transport depend on the dynamical conformational states of the filament. We characterize these states using filament writhe as an order parameter and identify ones yielding maxima in speed and efficiency of transport. The transport mechanism reported here has a remarkable resemblance to the flagellar propulsion of microorganisms which suggests its utility in biomimetic systems.

  8. Colloidal transport by active filaments

    Science.gov (United States)

    Manna, Raj Kumar; Kumar, P. B. Sunil; Adhikari, R.

    2017-01-01

    Enhanced colloidal transport beyond the limit imposed by diffusion is usually achieved through external fields. Here, we demonstrate the ballistic transport of a colloidal sphere using internal sources of energy provided by an attached active filament. The latter is modeled as a chain of chemo-mechanically active beads connected by potentials that enforce semi-flexibility and self-avoidance. The fluid flow produced by the active beads and the forces they mediate are explicitly taken into account in the overdamped equations of motion describing the colloid-filament assembly. The speed and efficiency of transport depend on the dynamical conformational states of the filament. We characterize these states using filament writhe as an order parameter and identify ones yielding maxima in speed and efficiency of transport. The transport mechanism reported here has a remarkable resemblance to the flagellar propulsion of microorganisms which suggests its utility in biomimetic systems.

  9. COLLOID RELEASE FROM DIFFERENT SOIL DEPTH

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2013-01-01

    Full Text Available Naturally occurring clay colloidal particles are heavily involved in sediment processes in the subsurface soil. Due to the import ance of these processes in the subsurface environment, the transport of clay colloidal particles has been studied in several disciplines, including soil sciences, petr ology, hydrology, etc. Specifically, in environmental engineering, clay colloid re lease and transport in the sediments have been extensively investigated, which are motiv ated by environmental concerns such as colloid-facilitated contaminant transport in groundwater and the subsurface soil. Clay colloid release is resulted from physical alteration of subsurface sediments. Despite the potential importance of clay colloid activiti es, the detailed mechanisms of release and transport of clay colloidal particles with in natural sediments are poorly understood. Pore medium structure, properties and flow dynamics, etc. are factors that affect clay colloid generation, mobilization, and subse quent transport. Possible mechanisms of clay colloid generation in the sediments in clude precipitation, erosion and mobilization by changes in pore water chemistry and clay colloid release depends on a balance of applied hydrodynamic and resisting adhesive torques and forces. The coupled role of pore water chemistry and fluid hydrodynamics thus play key roles in controlling clay colloid release and transport in the sediment s. This paper investigated clay colloidal particle release and transport, especially th e colloidal particle release mechanisms as well as the process modeling in the sediments. In this research, colloidal particle release from intact sediment columns with variable length was examined and colloidal particle release curves were simulated using an im plicit, finite-difference scheme. Colloidal particle release rate coefficient was found to be an exponential function of the sediment depth. The simulated results demonstrated that transport parameters were

  10. Self-Assembly of Faceted Colloidal Particles

    NARCIS (Netherlands)

    Gantapara, A.P.

    2015-01-01

    A colloidal dispersion consists of insoluble microscopic particles that are suspended in a solvent. Typically, a colloid is a particle for which at least one of its dimension is within the size range of a nanometer to a micron. Due to collisions with much smaller solvent molecules, colloids perform

  11. Colloid formation during waste glass corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Mertz, C.J.; Buck, E.C.; Fortner, J.A.; Bates, J.K.

    1996-05-01

    The long-term behavior of nuclear waste glass in a geologic repository may require a technical consideration of the role of colloids in the release and transport of radionuclides. The neglect of colloidal properties in assessing the near- and far-field migration behavior of actinides may lead to significant underestimates and poor predictions of biosphere exposure from high-level waste (HLW) disposal. Existing data on colloid-facilitated transport suggests that radionuclide migration may be enhanced, but the importance of colloids is not adequately assessed. Indeed, the occurrence of radionuclide transport, attributed to colloidal species, has been reported at Mortandad Canyon, Los Alamos and at the Nevada Test Site; both unsaturated regions are similar to the proposed HLW repository at Yucca Mountain. Although some developments have been made on understanding the transport characteristics of colloids, the characterization of colloids generated from the corrosion of the waste form has been limited. Colloids are known to incorporate radionuclides either from hydrolysis of dissolved species (real colloids) or from adsorption of dissolved species onto existing groundwater colloids (pseudocolloids); however, these colloids may be considered secondary and solubility limited when compared to the colloids generated during glass alteration.

  12. The colloid hematite particle migration through the unsaturated porous bed at the presence of biosurfactants.

    Science.gov (United States)

    Pawlowska, Agnieszka; Sznajder, Izabela; Sadowski, Zygmunt

    2017-07-01

    Colloidal particles have an ability to sorb heavy metals, metalloids, and organic compounds (e.g. biosurfactants) present in soil and groundwater. The pH and ionic strength changes may promote release of such particles causing potential contaminant transport. Therefore, it is very important to know how a colloid particle-mineral particle and colloid-mineral-biosurfactant system behaves in the natural environment. They can have negative impact on the environment and human health. This study highlighted the influence of biosurfactants produced by Pseudomonas aeruginosa on the transport of colloidal hematite (α-Fe 2 O 3 ) through porous bed (materials collected from the Szklary and Zloty Stok solid waste heaps from Lower Silesia, Poland). Experiments were conducted using column set in two variants: colloid solution with porous bed and porous bed with adsorbed biosurfactants, in the ionic strengths of 5 × 10 -4 and 5 × 10 -3  M KCl. The zeta potential of mineral materials and colloidal hematite, before and after adsorption of biosurfactant, was determined. Obtained results showed that reduction in ionic strength facilitates colloidal hematite transport through the porous bed. The mobility of colloidal hematite was higher when the rhamnolipid adsorbed on the surface of mineral grain.

  13. Modeling colloid-facilitated transport of multi-species contaminants in unsaturated porous media

    Science.gov (United States)

    Massoudieh, Arash; Ginn, Timothy R.

    2007-07-01

    Colloid-facilitated transport has been recognized as a potentially important and overlooked contaminant transport process. In particular, it has been observed that conventional two phase sorption models are often unable to explain transport of highly sorbing compounds in the subsurface appropriately in the presence of colloids. In this study a one-dimensional model for colloid-facilitated transport of chemicals in unsaturated porous media is developed. The model has parts for simulating coupled flow, and colloid transport and dissolved and colloidal contaminant transport. Richards' equation is solved to model unsaturated flow, and the effect of colloid entrapment and release on porosity and hydraulic conductivity of the porous media is incorporated into the model. Both random sequential adsorption and Langmuir approaches have been implemented in the model in order to incorporate the effect of surface jamming. The concept of entrapment of colloids into the air-water interface is used for taking into account the effect of retardation caused due to existence of the air phase. A non-equilibrium sorption approach with options of linear and Langmuir sorption assumptions are implemented that can represent the competition and site saturation effects on sorption of multiple compounds both to the solid matrix and to the colloidal particles. Several demonstration calculations are performed and the conditions in which the non-equilibrium model can be approximated by an equilibrium model are also studied.

  14. Modeling colloid-facilitated transport of multi-species contaminants in unsaturated porous media.

    Science.gov (United States)

    Massoudieh, Arash; Ginn, Timothy R

    2007-07-17

    Colloid-facilitated transport has been recognized as a potentially important and overlooked contaminant transport process. In particular, it has been observed that conventional two phase sorption models are often unable to explain transport of highly sorbing compounds in the subsurface appropriately in the presence of colloids. In this study a one-dimensional model for colloid-facilitated transport of chemicals in unsaturated porous media is developed. The model has parts for simulating coupled flow, and colloid transport and dissolved and colloidal contaminant transport. Richards' equation is solved to model unsaturated flow, and the effect of colloid entrapment and release on porosity and hydraulic conductivity of the porous media is incorporated into the model. Both random sequential adsorption and Langmuir approaches have been implemented in the model in order to incorporate the effect of surface jamming. The concept of entrapment of colloids into the air-water interface is used for taking into account the effect of retardation caused due to existence of the air phase. A non-equilibrium sorption approach with options of linear and Langmuir sorption assumptions are implemented that can represent the competition and site saturation effects on sorption of multiple compounds both to the solid matrix and to the colloidal particles. Several demonstration calculations are performed and the conditions in which the non-equilibrium model can be approximated by an equilibrium model are also studied.

  15. Insights into the sonochemical synthesis and properties of salt-free intrinsic plutonium colloids

    Science.gov (United States)

    Dalodière, Elodie; Virot, Matthieu; Morosini, Vincent; Chave, Tony; Dumas, Thomas; Hennig, Christoph; Wiss, Thierry; Dieste Blanco, Oliver; Shuh, David K.; Tyliszcak, Tolek; Venault, Laurent; Moisy, Philippe; Nikitenko, Sergey I.

    2017-03-01

    Fundamental knowledge on intrinsic plutonium colloids is important for the prediction of plutonium behaviour in the geosphere and in engineered systems. The first synthetic route to obtain salt-free intrinsic plutonium colloids by ultrasonic treatment of PuO2 suspensions in pure water is reported. Kinetics showed that both chemical and mechanical effects of ultrasound contribute to the mechanism of Pu colloid formation. In the first stage, fragmentation of initial PuO2 particles provides larger surface contact between cavitation bubbles and solids. Furthermore, hydrogen formed during sonochemical water splitting enables reduction of Pu(IV) to more soluble Pu(III), which then re-oxidizes yielding Pu(IV) colloid. A comparative study of nanostructured PuO2 and Pu colloids produced by sonochemical and hydrolytic methods, has been conducted using HRTEM, Pu LIII-edge XAS, and O K-edge NEXAFS/STXM. Characterization of Pu colloids revealed a correlation between the number of Pu-O and Pu-Pu contacts and the atomic surface-to-volume ratio of the PuO2 nanoparticles. NEXAFS indicated that oxygen state in hydrolytic Pu colloid is influenced by hydrolysed Pu(IV) species to a greater extent than in sonochemical PuO2 nanoparticles. In general, hydrolytic and sonochemical Pu colloids can be described as core-shell nanoparticles composed of quasi-stoichiometric PuO2 cores and hydrolyzed Pu(IV) moieties at the surface shell.

  16. Electronically conductive perovskite-based oxide nanoparticles and films for optical sensing applications

    Science.gov (United States)

    Ohodnicki, Jr., Paul R; Schultz, Andrew M

    2015-04-28

    The disclosure relates to a method of detecting a change in a chemical composition by contacting a electronically conducting perovskite-based metal oxide material with a monitored stream, illuminating the electronically conducting perovskite-based metal oxide with incident light, collecting exiting light, monitoring an optical signal based on a comparison of the incident light and the exiting light, and detecting a shift in the optical signal. The electronically conducting perovskite-based metal oxide has a perovskite-based crystal structure and an electronic conductivity of at least 10.sup.-1 S/cm, where parameters are specified at the gas stream temperature. The electronically conducting perovskite-based metal oxide has an empirical formula A.sub.xB.sub.yO.sub.3-.delta., where A is at least a first element at the A-site, B is at least a second element at the B-site, and where 0.8perovskite-based oxides include but are not limited to La.sub.1-xSr.sub.xCoO.sub.3, La.sub.1-xSr.sub.xMnO.sub.3, LaCrO.sub.3, LaNiO.sub.3, La.sub.1-xSr.sub.xMn.sub.1-yCr.sub.yO.sub.3, SrFeO.sub.3, SrVO.sub.3, La-doped SrTiO.sub.3, Nb-doped SrTiO.sub.3, and SrTiO.sub.3-.delta..

  17. Tunnel conductance of Watson-Crick nucleoside-base pairs from telegraph noise

    Energy Technology Data Exchange (ETDEWEB)

    Chang Shuai; He Jin; Lin Lisha; Zhang Peiming; Liang Feng; Huang Shuo; Lindsay, Stuart [Biodesign Institute, Arizona State University, Tempe, AZ 85287 (United States); Young, Michael [Department of Physics, Arizona State University, Tempe, AZ 85287 (United States)], E-mail: Stuart.Lindsay@asu.edu

    2009-05-06

    The use of tunneling signals to sequence DNA is presently hampered by the small tunnel conductance of a junction spanning an entire DNA molecule. The design of a readout system that uses a shorter tunneling path requires knowledge of the absolute conductance across base pairs. We have exploited the stochastic switching of hydrogen-bonded DNA base-nucleoside pairs trapped in a tunnel junction to determine the conductance of individual molecular pairs. This conductance is found to be sensitive to the geometry of the junction, but a subset of the data appears to come from unstrained molecular pairs. The conductances determined from these pairs are within a factor of two of the predictions of density functional calculations. The experimental data reproduces the counterintuitive theoretical prediction that guanine-deoxycytidine pairs (3 H-bonds) have a smaller conductance than adenine-thymine pairs (2 H-bonds). A bimodal distribution of switching lifetimes shows that both H-bonds and molecule-metal contacts break.

  18. Tunnel conductance of Watson-Crick nucleoside-base pairs from telegraph noise

    International Nuclear Information System (INIS)

    Chang Shuai; He Jin; Lin Lisha; Zhang Peiming; Liang Feng; Huang Shuo; Lindsay, Stuart; Young, Michael

    2009-01-01

    The use of tunneling signals to sequence DNA is presently hampered by the small tunnel conductance of a junction spanning an entire DNA molecule. The design of a readout system that uses a shorter tunneling path requires knowledge of the absolute conductance across base pairs. We have exploited the stochastic switching of hydrogen-bonded DNA base-nucleoside pairs trapped in a tunnel junction to determine the conductance of individual molecular pairs. This conductance is found to be sensitive to the geometry of the junction, but a subset of the data appears to come from unstrained molecular pairs. The conductances determined from these pairs are within a factor of two of the predictions of density functional calculations. The experimental data reproduces the counterintuitive theoretical prediction that guanine-deoxycytidine pairs (3 H-bonds) have a smaller conductance than adenine-thymine pairs (2 H-bonds). A bimodal distribution of switching lifetimes shows that both H-bonds and molecule-metal contacts break.

  19. Polypyrrole salts and bases: superior conductivity of nanotubes and their stability towards the loss of conductivity by deprotonation

    Czech Academy of Sciences Publication Activity Database

    Stejskal, Jaroslav; Trchová, Miroslava; Bober, Patrycja; Morávková, Zuzana; Kopecký, D.; Vrňata, M.; Prokeš, J.; Varga, M.; Watzlová, E.

    2016-01-01

    Roč. 6, č. 91 (2016), s. 88382-88391 ISSN 2046-2069 R&D Projects: GA ČR(CZ) GA13-00270S Institutional support: RVO:61389013 Keywords : polypyrrole salt * polypyrrole base * methyl orange Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.108, year: 2016

  20. Bonding assembled colloids without loss of colloidal stability

    NARCIS (Netherlands)

    Vutukuri, H.R.; Stiefelhagen, J.C.P.; Vissers, T; Imhof, A.; van Blaaderen, A.

    2012-01-01

    In recent years the diversity of self-assembled colloidal structures has strongly increased, as it is fueled by a wide range of applications in materials science and also in soft condensed-matter physics.[1–4] Some potential applications include photonic bandgap (PBG) crystals, materials for

  1. Highly Conductive, Transparent Flexible Films Based on Metal Nanoparticle-Carbon Nanotube Composites

    Directory of Open Access Journals (Sweden)

    Wen-Yin Ko

    2013-01-01

    Full Text Available Metallic nanoparticles decorated on MWCNTs based transparent conducting thin films (TCFs show a cheap and efficient option for the applications in touch screens and the replacement of the ITO film because of their interesting properties of electrical conductivity, mechanical property, chemical inertness, and other unique properties, which may not be accessible by their individual components. However, a great challenge that always remains is to develop effective ways to prepare junctions between metallic nanoparticles and MWCNTs for the improvement of high-energy barriers, high contact resistances, and weak interactions which could lead to the formation of poor conducting pathways and result in the CNT-based devices with low mechanical flexibility. Herein, we not only discuss recent progress in the preparation of MNP-CNT flexible TCFs but also describe our research studies in the relevant areas. Our result demonstrated that the MNP-CNT flexible TCFs we prepared could achieve a highly electrical conductivity with the sheet resistance of ~100 ohm/sq with ~80% transmittance at 550 nm even after being bent 500 times. This electrical conductivity is much superior to the performances of other MWCNT-based transparent flexible films, making it favorable for next-generation flexible touch screens and optoelectronic devices.

  2. Scratch-resistant, highly conductive, and high-strength carbon nanotube-based composite yarns.

    Science.gov (United States)

    Liu, Kai; Sun, Yinghui; Lin, Xiaoyang; Zhou, Ruifeng; Wang, Jiaping; Fan, Shoushan; Jiang, Kaili

    2010-10-26

    High-strength and conductive carbon nanotube (CNT) yarns are very attractive in many potential applications. However, there is a difficulty when simultaneously enhancing the strength and conductivity of CNT yarns. Adding some polymers into CNT yarns to enhance their strength will decrease their conductivity, while treating them in acid or coating them with metal nanoparticles to enhance their conductivity will reduce their strength. To overcome this difficulty, here we report a method to make high-strength and highly conductive CNT-based composite yarns by using a continuous superaligned CNT (SACNT) yarn as a conductive framework and then inserting polyvinyl alcohol (PVA) into the intertube spaces of the framework through PVA/dimethyl sulphoxide solution to enhance the strength of yarns. The as-produced CNT/PVA composite yarns possess very high tensile strengths up to 2.0 GPa and Young's moduli more than 120 GPa, much higher than those of the CNT/PVA yarns reported. The electric conductivity of as-produced composite yarns is as high as 9.2 × 10(4) S/m, comparable to HNO(3)-treated or Au nanoparticle-coated CNT yarns. These composite yarns are flexible, lightweight, scratch-resistant, very stable in the lab environment, and resistant to extremely humid ambient and as a result can be woven into high-strength and heatable fabrics, showing potential applications in flexible heaters, bullet-proof vests, radiation protection suits, and spacesuits.

  3. 76 FR 46668 - Business Conduct Standards for Security-Based Swap Dealers and Major Security-Based Swap...

    Science.gov (United States)

    2011-08-03

    ... SECURITIES AND EXCHANGE COMMISSION 17 CFR Part 240 [Release No. 34-64766; File No. S7-25-11] RIN 3235-AL10 Business Conduct Standards for Security-Based Swap Dealers and Major Security-Based Swap Participants Correction In proposed rule document number 2011-16758, appearing on pages 42396-42455 in the...

  4. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1996-06-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation of irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  5. Effects of neutron irradiation on thermal conductivity of SiC-based composites and monolithic ceramics

    International Nuclear Information System (INIS)

    Senor, D.J.; Youngblood, G.E.; Moore, C.E.; Trimble, D.J.; Woods, J.J.

    1997-05-01

    A variety of SiC-based composites and monolithic ceramics were characterized by measuring their thermal diffusivity in the unirradiated, thermal annealed, and irradiated conditions over the temperature range 400 to 1,000 C. The irradiation was conducted in the EBR-II to doses of 33 and 43 dpa-SiC (185 EFPD) at a nominal temperature of 1,000 C. The annealed specimens were held at 1,010 C for 165 days to approximately duplicate the thermal exposure of the irradiated specimens. Thermal diffusivity was measured using the laser flash method, and was converted to thermal conductivity using density data and calculated specific heat values. Exposure to the 165 day anneal did not appreciably degrade the conductivity of the monolithic or particulate-reinforced composites, but the conductivity of the fiber-reinforced composites was slightly degraded. The crystalline SiC-based materials tested in this study exhibited thermal conductivity degradation after irradiation, presumably caused by the presence of irradiation-induced defects. Irradiation-induced conductivity degradation was greater at lower temperatures, and was typically more pronounced for materials with higher unirradiated conductivity. Annealing the irradiated specimens for one hour at 150 C above the irradiation temperature produced an increase in thermal conductivity, which is likely the result of interstitial-vacancy pair recombination. Multiple post-irradiation anneals on CVD β-SiC indicated that a portion of the irradiation-induced damage was permanent. A possible explanation for this phenomenon was the formation of stable dislocation loops at the high irradiation temperature and/or high dose that prevented subsequent interstitial/vacancy recombination

  6. Preparation and Properties of Silver Nanowire-Based Transparent Conductive Composite Films

    Science.gov (United States)

    Tian, Ji-Li; Zhang, Hua-Yu; Wang, Hai-Jun

    2016-06-01

    Silver nanowire-based transparent conductive composite films with different structures were successfully prepared using various methods, including liquid polyol, magnetron sputtering and spin coating. The experimental results revealed that the optical transmittance of all different structural composite films decreased slightly (1-3%) compared to pure films. However, the electrical conductivity of all composite films had a great improvement. Under the condition that the optical transmittance was greater than 78% over the wavelength range of 400-800 nm, the AgNW/PVA/AgNW film became a conductor, while the AZO/AgNW/AZO film and the ITO/AgNW/ITO film showed 88.9% and 94% reductions, respectively, for the sheet resistance compared with pure films. In addition, applying a suitable mechanical pressure can improve the conductivity of AgNW-based composite films.

  7. Reversible light-controlled conductance switching of azobenzene-based metal/polymer nanocomposites

    International Nuclear Information System (INIS)

    Pakula, Christina; Zaporojtchenko, Vladimir; Strunskus, Thomas; Faupel, Franz; Zargarani, Dordaneh; Herges, Rainer

    2010-01-01

    We present a new concept of light-controlled conductance switching based on metal/polymer nanocomposites with dissolved chromophores that do not have intrinsic current switching ability. Photoswitchable metal/PMMA nanocomposites were prepared by physical vapor deposition of Au and Pt clusters, respectively, onto spin-coated thin poly(methylmethacrylate) films doped with azo-dye molecules. High dye concentrations were achieved by functionalizing the azo groups with tails and branches, thus enhancing solubility. The composites show completely reversible optical switching of the absorption bands upon alternating irradiation with UV and blue light. We also demonstrate reversible light-controlled conductance switching. This is attributed to changes in the metal cluster separation upon isomerization based on model experiments where analogous conductance changes were induced by swelling of the composite films in organic vapors and by tensile stress.

  8. Vertically Conductive Single-Crystal SiC-Based Bragg Reflector Grown on Si Wafer

    Science.gov (United States)

    Massoubre, David; Wang, Li; Hold, Leonie; Fernandes, Alanna; Chai, Jessica; Dimitrijev, Sima; Iacopi, Alan

    2015-11-01

    Single-crystal silicon carbide (SiC) thin-films on silicon (Si) were used for the fabrication and characterization of electrically conductive distributed Bragg reflectors (DBRs) on 100 mm Si wafers. The DBRs, each composed of 3 alternating layers of SiC and Al(Ga)N grown on Si substrates, show high wafer uniformity with a typical maximum reflectance of 54% in the blue spectrum and a stopband (at 80% maximum reflectance) as large as 100 nm. Furthermore, high vertical electrical conduction is also demonstrated resulting to a density of current exceeding 70 A/cm2 above 1.5 V. Such SiC/III-N DBRs with high thermal and electrical conductivities could be used as pseudo-substrate to enhance the efficiency of SiC-based and GaN-based optoelectronic devices on large Si wafers.

  9. Multi-channel conduction in redox-based resistive switch modelled using quantum point contact theory

    Energy Technology Data Exchange (ETDEWEB)

    Miranda, E., E-mail: enrique.miranda@uab.cat; Suñé, J. [Departament d' Enginyeria Electrònica, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallés, Barcelona (Spain); Mehonic, A.; Kenyon, A. J. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom)

    2013-11-25

    A simple analytic model for the electron transport through filamentary-type structures in Si-rich silica (SiO{sub x})-based resistive switches is proposed. The model is based on a mesoscopic description and is able to account for the linear and nonlinear components of conductance that arise from both fully and partially formed conductive channels spanning the dielectric film. Channels are represented by arrays of identical scatterers whose number and quantum transmission properties determine the current magnitude in the low and high resistance states. We show that the proposed model not only reproduces the experimental current-voltage (I-V) characteristics but also the normalized differential conductance (dln(I)/dln(V)-V) curves of devices under test.

  10. Forward Conduction Mode Controlled Piezoelectric Transformer-Based PFC LED Drive

    DEFF Research Database (Denmark)

    Roedgaard, M. S.; Weirich, M.; Andersen, M. A. E.

    2013-01-01

    priced market. In this paper, a new forward conduction mode (FCM) control method for piezoelectric transformer (PT)-based power converters is proposed. A PT-based LED drive facilitating passive PFC is developed, utilizing and validating the FCM control method. The drive utilizes an inductorless half...... LED drive has been developed, supplied from 230-V 50-Hz ac mains, achieving a power factor of 0.96....

  11. 5 CFR 9901.343 - Pay reduction based on unacceptable performance and/or conduct.

    Science.gov (United States)

    2010-01-01

    ... performance and/or conduct. 9901.343 Section 9901.343 Administrative Personnel DEPARTMENT OF DEFENSE HUMAN RESOURCES MANAGEMENT AND LABOR RELATIONS SYSTEMS (DEPARTMENT OF DEFENSE-OFFICE OF PERSONNEL MANAGEMENT) DEPARTMENT OF DEFENSE NATIONAL SECURITY PERSONNEL SYSTEM (NSPS) Pay and Pay Administration Performance-Based...

  12. Performance Improvement by Layout Designs of Conductive Polymer Microelectrode Based Impedimetric Biosensors

    DEFF Research Database (Denmark)

    Rosati, Giulio; Daprà, Johannes; Cherré, Solène

    2014-01-01

    In this work we present a theoretical, computational, and experimental evaluation of the performance of an impedimetric biosensor based on interdigitated conductive polymer (PEDOT:TsO) microelectrodes in a microfluidic system. The influence of the geometry of the electrodes and microchannels on t...

  13. Conductivity Enhancement of Binder-Based Graphene Inks by Photonic Annealing and Subsequent Compression Rolling

    NARCIS (Netherlands)

    Arapov, K.; Bex, G.; Hendriks, R.; Rubingh, E.; Abbel, R.; de With, G.; Friedrich, H.

    2016-01-01

    This paper describes a combination of photonic annealing and compression rolling to improve the conductive properties of printed binder-based graphene inks. High-density light pulses result in temperatures up to 500 °C that along with a decrease of resistivity lead to layer expansion. The structural

  14. A Hot-Wire Method Based Thermal Conductivity Measurement Apparatus for Teaching Purposes

    Science.gov (United States)

    Alvarado, S.; Marin, E.; Juarez, A. G.; Calderon, A.; Ivanov, R.

    2012-01-01

    The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer…

  15. Enhanced thermal conductivity of nano-SiC dispersed water based ...

    Indian Academy of Sciences (India)

    Silicon carbide (SiC) nanoparticle dispersed water based nanofluids were prepared using up to 0.1 vol% of nanoparticles. Use of suitable stirring routine ensured uniformity and stability of dispersion. Thermal conductivity ratio of nanofluid measured using transient hot wire device shows a significant increase of up to 12% ...

  16. Particle size effects in the thermal conductivity enhancement of copper-based nanofluids

    Directory of Open Access Journals (Sweden)

    Sahin Huseyin

    2011-01-01

    Full Text Available Abstract We present an analysis of the dispersion characteristics and thermal conductivity performance of copper-based nanofluids. The copper nanoparticles were prepared using a chemical reduction methodology in the presence of a stabilizing surfactant, oleic acid or cetyl trimethylammonium bromide (CTAB. Nanofluids were prepared using water as the base fluid with copper nanoparticle concentrations of 0.55 and 1.0 vol.%. A dispersing agent, sodium dodecylbenzene sulfonate (SDBS, and subsequent ultrasonication was used to ensure homogenous dispersion of the copper nanopowders in water. Particle size distribution of the copper nanoparticles in the base fluid was determined by dynamic light scattering. We found that the 0.55 vol.% Cu nanofluids exhibited excellent dispersion in the presence of SDBS. In addition, a dynamic thermal conductivity setup was developed and used to measure the thermal conductivity performance of the nanofluids. The 0.55 vol.% Cu nanofluids exhibited a thermal conductivity enhancement of approximately 22%. In the case of the nanofluids prepared from the powders synthesized in the presence of CTAB, the enhancement was approximately 48% over the base fluid for the 1.0 vol.% Cu nanofluids, which is higher than the enhancement values found in the literature. These results can be directly related to the particle/agglomerate size of the copper nanoparticles in water, as determined from dynamic light scattering.

  17. CSO pollution analysis based on conductivity and turbidity measurements and implications for application of RTC

    NARCIS (Netherlands)

    Rombouts, P.M.M.; Schilperoort, R.; Langeveld, J.G.; Clemens, F.H.L.R.

    2013-01-01

    The objective of this paper is to demonstrate the applicability of, and need for, surrogate sensors as robust sensors for water quality based RTC. For this purpose 1.5 years of level, conductivity (EC) and turbidity (TU) measurements at 9 combined sewer overflow (CSO) locations have been performed

  18. Molecular modeling of the conductivity changes of the emeraldine base polyaniline due to protonic acid doping

    NARCIS (Netherlands)

    Chen, X.; Yuan, C.A.; Wong, C.K.Y.; Zhang, G.

    2012-01-01

    We propose a molecular modeling strategy, which is capable of predicting the conductivity change of emeraldine base polyaniline polymer due to different degree of protonic acid doping. The method is comprised of two key steps: (1) generating the amorphous unit cells with given number of polymer

  19. Ionomeric membranes based on partially sulfonated poly(styrene) : synthesis, proton conduction and methanol permeation

    NARCIS (Netherlands)

    Picchioni, F.; Tricoli, V.; Carretta, N.

    2000-01-01

    Homogeneuosly sulfonated poly(styrene) (SPS) was prepared with various concentration of sulfonic acid groups in the base polymer. Membranes cast from these materials were investigated in relation to proton conductivity and methanol permeability in the temperature range from 20°C to 60°C. It was

  20. Inner Phases of Colloidal Hexagonal Spin Ice

    Science.gov (United States)

    Libál, A.; Nisoli, C.; Reichhardt, C. J. O.; Reichhardt, C.

    2018-01-01

    Using numerical simulations that mimic recent experiments on hexagonal colloidal ice, we show that colloidal hexagonal artificial spin ice exhibits an inner phase within its ice state that has not been observed previously. Under increasing colloid-colloid repulsion, the initially paramagnetic system crosses into a disordered ice regime, then forms a topologically charge ordered state with disordered colloids, and finally reaches a threefold degenerate, ordered ferromagnetic state. This is reminiscent of, yet distinct from, the inner phases of the magnetic kagome spin ice analog. The difference in the inner phases of the two systems is explained by their difference in energetics and frustration.

  1. A short textbook of colloid chemistry

    CERN Document Server

    Jirgensons, B

    1962-01-01

    A Short Textbook of Colloid Chemistry, Second Revised Edition details the factual aspect of colloid chemistry that includes the basic facts, established empirical and mathematical relationships, and practical applications. The chapters of the title are organized into two parts. In the first part, the text discusses the general concepts of colloid chemistry, such as the history and scope, basic terms, and basic methods in experiment with colloids. Part Two covers the technical aspect of colloid chemistry, such as the optical properties, electrical properties, and viscosity. The book will be of

  2. An Analytical Model of Thermal Conductivity for Carbon/Carbon Composites with Pitch-Based Matrix

    Directory of Open Access Journals (Sweden)

    Zhi-Hai Feng

    2015-01-01

    Full Text Available The carbon/carbon (C/C composites are composed of carbon fibers, carbon matrix, and pores and cracks, which have been successfully used in various aerospace applications. In this paper, nanoscale submodel is proposed to describe the thermal conductivity of the matrix based on its microscopic structure, and then the submodel is incorporated into a microscale model to analytically predict the equivalent thermal conductivities of the composites by equivalent circuit approach. The results predicted by the present model agree well with those from the experimental measurements. Based on the model, the effects of the composite porosity as well as the thickness and porosity of the interface phase on the thermal performance of five composites are studied. It is found that the thermal conductivities show decreasing trends in responding to an increase in each of the three parameters. The composite porosity has a significant effect on the thermal conductivities both parallel and transverse to the fiber axis, while the thickness and the porosity of the interface phase remarkably affect the thermal conductivity only transverse to the fiber axis.

  3. Classification of materials for conducting spheroids based on the first order polarization tensor

    Science.gov (United States)

    Khairuddin, TK Ahmad; Mohamad Yunos, N.; Aziz, ZA; Ahmad, T.; Lionheart, WRB

    2017-09-01

    Polarization tensor is an old terminology in mathematics and physics with many recent industrial applications including medical imaging, nondestructive testing and metal detection. In these applications, it is theoretically formulated based on the mathematical modelling either in electrics, electromagnetics or both. Generally, polarization tensor represents the perturbation in the electric or electromagnetic fields due to the presence of conducting objects and hence, it also desribes the objects. Understanding the properties of the polarization tensor is necessary and important in order to apply it. Therefore, in this study, when the conducting object is a spheroid, we show that the polarization tensor is positive-definite if and only if the conductivity of the object is greater than one. In contrast, we also prove that the polarization tensor is negative-definite if and only if the conductivity of the object is between zero and one. These features categorize the conductivity of the spheroid based on in its polarization tensor and can then help to classify the material of the spheroid.

  4. Colloidal aspects of texture perception

    NARCIS (Netherlands)

    Vliet, van T.

    2010-01-01

    The perception of complex textures in food is strongly related to the way food is processed during eating, and is modulated by other basic characteristics, such as taste and aroma. An understanding at the colloidal level of the basic processes in the mouth is essential in order to link the

  5. Density, dynamic viscosity, and electrical conductivity of pyridinium-based hydrophobic ionic liquids

    International Nuclear Information System (INIS)

    Liu, Qing-Shan; Li, Pei-Pei; Welz-Biermann, Urs; Chen, Jian; Liu, Xiao-Xia

    2013-01-01

    Highlights: • Targets of this research are hydrophobic series ionic liquids. • Density, dynamic viscosity and electrical conductivity were determined. • Influences of methylene to properties were discussed. • Influences of methyl group on pyridinium ring position to properties were discussed. • Relationship of ρ, η and σ were described systematically. -- Abstract: Air and water stable hydrophobic ionic liquids (ILs) were synthesized: N-propyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide [C 3 3mpy][NTf 2 ], N-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide [C 6 3mpy][NTf 2 ], and N-hexyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide [C 6 4mpy][NTf 2 ]. Density, dynamic viscosity, and electrical conductivity of ILs were determined at atmospheric pressure in the temperature range of (278 to 353) K. The effects of methylene and methyl groups to density, dynamic viscosity, and electrical conductivity, respectively, were discussed. The thermal expansion coefficient, molecular volume, standard molar entropy, and lattice energy of the samples were estimated in terms of empirical and semi-empirical equations based on the density values. The temperature dependence on dynamic viscosity and electrical conductivity values of the ILs were discussed by Vogel–Fulcher–Tamman (VFT) and Arrhenius equations. The molar conductivities were calculated by density and electrical conductivity values

  6. Gamma- and electron dose response of the electrical conductivity of polyaniline based polymer blends

    International Nuclear Information System (INIS)

    Sevil, U.A.; Gueven, O.; Slezsak, I.

    2002-01-01

    Complete text of publication follows. Conducting polymers, also known as 'synthetic metals' have been the subject of widespread investigations over the past decade due to their very promising characteristics. Polyaniline (PANI) holds a special position among conducting polymers in that its most highly conducting doped form can be reached by protonic acid doping or oxidative doping. It was published earlier, that the electrical conductivity of some polyaniline based polymer composites increases to a significant extent when irradiated to gamma, electron or UV radiation. The aim of the present study was to measure the high frequency conductivity of blended films of PANI with poly(vinylchloride), PVC, and chlorinated poly(propylene) irradiated in air to different doses. In order to find the most suitable composition od these composites the mass percentage of PANI within the PPCl and PVC matrix was changed between 5 - 30%. These samples were then gamma irradiated and the induced electrical conductivity was measured in the 1 kHz - 1 MHz frequency range to determine the most sensitive evaluation conditions. After selecting both the most suitable measuring conditions as well as the blend compositions the dose response of the chosen samples was determined in the dose range of 10 - 250 kGy. With respect to potential dosimetry application the effect of electron irradiation, the effect of irradiation temperature and the stability of the irradiated samples have also been investigated

  7. Effective Thermal Conductivity of Open Cell Polyurethane Foam Based on the Fractal Theory

    Directory of Open Access Journals (Sweden)

    Kan Ankang

    2013-01-01

    Full Text Available Based on the fractal theory, the geometric structure inside an open cell polyurethane foam, which is widely used as adiabatic material, is illustrated. A simplified cell fractal model is created. In the model, the method of calculating the equivalent thermal conductivity of the porous foam is described and the fractal dimension is calculated. The mathematical formulas for the fractal equivalent thermal conductivity combined with gas and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity, are deduced. However, the total effective heat flux is the summation of the heat conduction by the solid phase and the gas in pores, the radiation, and the convection between gas and solid phase. Fractal mathematical equation of effective thermal conductivity is derived with fractal dimension and vacancy porosity in the cell body. The calculated results have good agreement with the experimental data, and the difference is less than 5%. The main influencing factors are summarized. The research work is useful for the enhancement of adiabatic performance of foam materials and development of new materials.

  8. Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system.

    Science.gov (United States)

    Ha, Sung Min; Kwon, O Hwan; Oh, Yu Gyeong; Kim, Yong Seok; Lee, Sung-Goo; Won, Jong Chan; Cho, Kwang Soo; Kim, Byoung Gak; Yoo, Youngjae

    2015-12-01

    We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K) -1 , which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis-Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

  9. Improved thermal conductivity of Ag decorated carbon nanotubes water based nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Farbod, Mansoor, E-mail: farbod_m@scu.ac.ir; Ahangarpour, Ameneh

    2016-12-16

    The effect of Ag decoration of carbon nanotubes on thermal conductivity enhancement of Ag decorated MWCNTs water based nanofluids has been investigated. The pristine and functionalized MWCNTs were decorated with Ag nanoparticles by mass ratios of 1%, 2% and 4% and used to prepare water based nanofluids with 0.1 vol.%. An enhancement of 1–20.4 percent in thermal conductivity was observed. It was found that the decoration of functionalized MWCNTs can increase the thermal conductivity about 0.16–8.02 percent compared to the undecorated ones. The maximum enhancement of 20.4% was measured for the sample containing 4 wt.% Ag at 40 °C. - Highlights: • MWCNTs were decorated with Ag nanoparticles by the mass ratios of 1, 2 and 4%. • The decorated CNTs were used to prepare water based nanofluids with 0.1 Vol.%. • 1–20.4% increase was observed in thermal conductivity (TC) compared to pure water. • Ag decorated CNTs increased TC of nanofluid up to 8% compared to CNTs nanofluid.

  10. Development of a team-based framework for conducting self-assessment of Continuous Improvement

    DEFF Research Database (Denmark)

    Jørgensen, Frances; Gertsen, Frank; Boer, Harry

    2004-01-01

    The study presented in this article is based on two basic premises. First, successful continuous improvement (CI) is dependent on shop floor level involvement and participation in improvement efforts. Second, the term "self-assessment" clearly implies that those whose performance is being measured......, and who are involved in conducting the assessment process. Excerpts from longitudinal case studies in a single Danish manufacturing organization demonstrate how teams involved in the process of conducting self-assessment of CI developed a better understanding of the basic principles of CI. Furthermore...

  11. Lithium ion conducting biopolymer electrolyte based on pectin doped with Lithium nitrate

    Science.gov (United States)

    Manjuladevi, R.; Selvin, P. Christopher; Selvasekarapandian, S.; Shilpa, R.; Moniha, V.

    2018-04-01

    The Biopolymer electrolyte based on pectin doped with lithium nitrate of different concentrations have been prepared by solution casting technique. The decrease in crystalline nature of the biopolymer has been identified by XRD analyses. The complex formation between the polymer and the salt has been revealed using FTIR analysis. The ionic conductivity has been explored using A.C. impedance spectroscopy which reveals that the biopolymer containing 30 wt% Pectin: 70wt%LiNO3 has highest ionic conductivity of 3.97 × 10-3 Scm-1.

  12. Radiolytic synthesis and characterization of PVA and chitosan based conductive polymer membranes for alkaline fuel cells

    Directory of Open Access Journals (Sweden)

    Stoševski Ivan D.

    2014-01-01

    Full Text Available Poly(vinyl alcohol (PVA and chitosan (CS based polymer membranes for alkaline fuel cells were synthesized by gamma irradiation method. They were swollen with 6 M KOH solution and their ionic conductivity and gas permeance were investigated as a function of temperature. They show high ionic conductivities at room temperature, which wasn't reduced over a period of few months. No gas flow through membranes was detected at any temperature and pressure. These properties show that the membranes could be potentially applied in alkaline fuel cells.

  13. Glass/Jamming Transition in Colloidal Aggregation

    Science.gov (United States)

    Segre, Philip N.; Prasad, Vikram; Weitz, David A.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have studied colloidal aggregation in a model colloid plus polymer system with short-range attractive interactions. By varying the colloid concentration and the strength of the attraction, we explored regions where the equilibrium phase is expected to consist of colloidal crystallites in coexistance with colloidal gas (i.e. monomers). This occurs for moderate values of the potential depth, U approximately equal to 2-5 kT. Crystallization was not always observed. Rather, over an extended sub-region two new metastable phases appear, one fluid-like and one solid-like. These were examined in detail with light scattering and microscopy techniques. Both phases consist of a near uniform distribution of small irregular shaped clusters of colloidal particles. The dynamical and structural characteristics of the ergodic-nonergodic transition between the two phases share much in common with the colloidal hard sphere glass transition.

  14. COLLOIDS IN SEPTIC TANK EFFLUENT AND THEIR INFLUENCE ON FILTER PERMEABILITY

    Directory of Open Access Journals (Sweden)

    Marcin Spychała

    2015-09-01

    Full Text Available The aim of the study was to evaluate the content of colloids in septic tank effluent and their impact on textile filter permeability. Measurements were performed on septic tank effluent without suspended solids but containing colloids and without colloids - including only dissolved substances (filtered by micro-filters and centrifuged. The study was conducted on unclogged and clogged textile filter coupons. During the study the following measurements were determined: turbidity, chemical oxygen demand and hydraulic conductivity of textile filter coupons. The colloid size range was assumed to be less than 1.2 microns according to the literature. Despite the relatively low content in the septic tank effluent the colloids played an important role in the clogging process. Both the filtering media, filled with low (unclogged and high content of biomass (clogged were sensitive to the clogging process of colloid acceleration due to the possibility of small diameter pore closure and oxygen access termination. Moreover, small size pores were probably sensitive to closing or bridging by small size colloidal particles.

  15. Colloids and Radionuclide Transport: A Field, Experimental and Modeling Effort

    Science.gov (United States)

    Zhao, P.; Zavarin, M.; Sylwester, E. E.; Allen, P. G.; Williams, R. W.; Kersting, A. B.

    2002-05-01

    Natural inorganic colloids (colloid-facilitated transport to the transport of low-solubility actinides, such as Pu, is still not well understood. In an effort to better understand the dominant geochemical mechanisms that control Pu transport, we have performed a series of sorption/desorption experiments using mineral colloids. We focused on natural colloidal minerals present in water samples collected from both saturated and vadose zone waters at the Nevada Test Site. These minerals include zeolites, clays, silica, Mn-oxides, Fe-oxides, and calcite. X-ray absorption fine-structure spectroscopy ( both XANES and EXAFS) was performed in order to characterize the speciation of sorbed plutonium. The XANES spectra show that only Pu(IV) was detected (within experimental error) on these mineral surfaces when the starting Pu oxidation state was +5, indicating that Pu(V) was reduced to Pu(IV) during sorption. The EXAFS detected Pu-M and Pu-C interactions (where M=Fe, Mn, or Si) indicating Pu(IV) surface complexation along with carbonate ternary complex formation on most of the minerals tested. Although the plutonium sorption as Pu(IV) species is mineral independent, the actual sorption paths are different for different minerals. The sorption rates were compared to the rates of plutonium disproportionation under similar conditions. The batch sorption/desorption experiments of Pu(IV) and Pu(V) onto colloidal zeolite (clinoptilolite, colloids particle size 171 ñ 25 nm) were conducted in synthetic groundwater (similar to J-13, Yucca Mountain standard) with a pH range from 4 to 10 and initial plutonium concentration of 10-9 M. The results show that Pu(IV) sorption takes place within an hour, while the rates of Pu(V) sorption onto the colloids is much slower and mineral dependent. The kinetic results from the batch sorption/desorption experiments, coupled with redox kinetics of plutonium in solution will be used in geochemical modeling of Pu surface complexation to colloids and

  16. Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Ganjali

    2008-04-01

    Full Text Available Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylenes, poly(pyrroles, poly(thiophenes, poly(terthiophenes, poly(anilines, poly(fluorines, poly(3-alkylthiophenes, polytetrathiafulvalenes, polynapthalenes, poly(p-phenylene sulfide, poly(p-phenylenevinylenes, poly(3,4-ethylenedioxythiophene, polyparaphenylene, polyazulene, polyparaphenylene sulfide, polycarbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs, i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE, Single-Piece ISE (SPISE, Conducting Polymer (CP-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

  17. Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade.

    Science.gov (United States)

    Faridbod, Farnoush; Norouzi, Parviz; Dinarvand, Rassoul; Ganjali, Mohammad Reza

    2008-04-03

    Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, polynapthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylenedioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, polycarbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed.

  18. Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

    International Nuclear Information System (INIS)

    Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.; Marks, Christopher A.; Jassby, David

    2017-01-01

    Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSE of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.

  19. Quality control in nerve conduction studies with coupled knowledge-based system approach.

    Science.gov (United States)

    Xiang, Y; Eisen, A; MacNeil, M; Beddoes, M P

    1992-02-01

    Contemporary equipment used for nerve conduction studies is usually capable of computerized measurement of latency, amplitude, duration, and area of nerve and muscle action potentials and resulting conduction velocities. Abnormalities can be due to technical error or disease. Identification of technical error is a major element of quality control in electromyography, and artificial intelligence could be useful for this purpose. We have developed a coupled knowledge-based prototype system (QUALICON) to assess the correctness of recording and stimulating characteristics in routine conduction studies. QUALICON extracts numeric features from CMAPs or SNAPs, which are translated into symbolic form to drive a Bayesian network. The network uses high-level knowledge to infer the quality of stimulating and recording electrode placement as well as polarity and stimulus strength making recommendations as to the likely technical error when abnormal potentials are detected. A preliminary assessment shows that QUALICON performs as well as manual assessment performed by professionals.

  20. Water-Based Fe2O3 Nanofluid Characterization: Thermal Conductivity and Viscosity Measurements and Correlation

    Directory of Open Access Journals (Sweden)

    L. Colla

    2012-01-01

    Full Text Available An experimental investigation on water-based nanofluids containing iron oxide (Fe2O3 in concentrations ranging between 5 and 20% in mass is presented. The purpose of this study is to measure thermal conductivity and dynamic viscosity of these fluids, as a starting point to study the heat transfer capability. The stability of the nanofluids was verified by pH and Zeta potential measurements. A dynamic light scattering (DLS technique was used to obtain the mean nanoparticle diameters. It was found that thermal conductivity of these nanofluids improved with temperature and particles concentration. The temperature and nanoparticle concentration effects on viscosity were analyzed, obtaining a significant increase with respect to water. All the fluids exhibited a Newtonian behaviour. The experimental values were compared with some theoretical models for both thermal conductivity and dynamic viscosity.

  1. Highly conductive, transparent flexible films based on open rings of multi-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Ko, Wen-Yin; Su, Jun-Wei; Guo, Chian-Hua; Fu, Shu-Juan; Hsu, Chuen-Yuan; Lin, Kuan-Jiuh

    2011-01-01

    Open rings of multi-walled carbon nanotubes were stacked to form porous networks on a poly(ethylene terephthalate) substrate to form a flexible conducting film (MWCNT-PET) with good electrical conductivity and transparency by a combination of ultrasonic atomization and spin-coating technique. To enhance the electric flexibility, we spin-coated a cast film of poly(vinyl alcohol) onto the MWCNT-PET substrate, which then underwent a thermo-compression process. Field-emission scanning electron microscopy of the cross-sectional morphology illustrates that the film has a robust network with a thickness of ∼ 175 nm, and it remarkably exhibits a sheet resistance of approximately 370 Ω/sq with ∼ 77% transmittance at 550 nm even after 500 bending cycles. This electrical conductivity is much superior to that of other MWCNT-based transparent flexible films.

  2. MREIT conductivity imaging based on the local harmonic Bz algorithm: Animal experiments

    Science.gov (United States)

    Jeon, Kiwan; Lee, Chang-Ock; Woo, Eung Je; Kim, Hyung Joong; Seo, Jin Keun

    2010-04-01

    From numerous numerical and phantom experiments, MREIT conductivity imaging based on harmonic Bz algorithm shows that it could be yet another useful medical imaging modality. However, in animal experiments, the conventional harmonic Bz algorithm gives poor results near boundaries of problematic regions such as bones, lungs, and gas-filled stomach, and the subject boundary where electrodes are not attached. Since the amount of injected current is low enough for the safety for in vivo animal, the measured Bz data is defected by severe noise. In order to handle such problems, we use the recently developed local harmonic Bz algorithm to obtain conductivity images in our ROI(region of interest) without concerning the defected regions. Furthermore we adopt a denoising algorithm that preserves the ramp structure of Bz data, which informs of the location and size of anomaly. Incorporating these efficient techniques, we provide the conductivity imaging of post-mortem and in vivo animal experiments with high spatial resolution.

  3. Colloidal Photoluminescent Amorphous Porous Silicon, Methods Of Making Colloidal Photoluminescent Amorphous Porous Silicon, And Methods Of Using Colloidal Photoluminescent Amorphous Porous Silicon

    KAUST Repository

    Chaieb, Sahraoui

    2015-04-09

    Embodiments of the present disclosure provide for a colloidal photoluminescent amorphous porous silicon particle suspension, methods of making a colloidal photoluminescent amorphous porous silicon particle suspension, methods of using a colloidal photoluminescent amorphous porous silicon particle suspension, and the like.

  4. Accelerated lattice Boltzmann model for colloidal suspensions rheology and interface morphology

    CERN Document Server

    Farhat, Hassan; Kondaraju, Sasidhar

    2014-01-01

    Colloids are ubiquitous in the food, medical, cosmetics, polymers, water purification, and pharmaceutical industries. The thermal, mechanical, and storage properties of colloids are highly dependent on their interface morphology and their rheological behavior. Numerical methods provide a convenient and reliable tool for the study of colloids. Accelerated Lattice Boltzmann Model for Colloidal Suspensions introduce the main building-blocks for an improved lattice Boltzmann–based numerical tool designed for the study of colloidal rheology and interface morphology. This book also covers the migrating multi-block used to simulate single component, multi-component, multiphase, and single component multiphase flows and their validation by experimental, numerical, and analytical solutions.   Among other topics discussed are the hybrid lattice Boltzmann method (LBM) for surfactant-covered droplets; biological suspensions such as blood; used in conjunction with the suppression of coalescence for investigating the...

  5. Compensating for Electrode Polarization in Dielectric Spectroscopy Studies of Colloidal Suspensions: Theoretical Assessment of Existing Methods

    Science.gov (United States)

    Chassagne, Claire; Dubois, Emmanuelle; Jiménez, María L.; van der Ploeg, J. P. M; van Turnhout, Jan

    2016-01-01

    Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP). In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical) with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed. PMID:27486575

  6. Three-Dimensional Radionuclide Transport Through the Unsaturated Zone of the Yucca Mountain Site 3 Colloids

    International Nuclear Information System (INIS)

    G. J. Moridis; Y. Seol

    2007-01-01

    The authors investigated colloid transport in the unsaturated fractured zone by means of three-dimensional site-scale numerical model under present-day climate infiltration, considering varying colloid diameters, kinetic declogging, and filtration. The radionuclide transport model was used to simulate continuous release of colloids into fractures throughout the proposed repository, in which any components of engineered barrier system such as waste package or drip shield were not considered. the results of the study indicate the importance of subsurface geology and site hydrology, i.e., the presence of faults (they dominate and control transport), fractures (the main migration pathways), and the relative distribution of zeolitic and vitric tuffs. The simulations indicate that (1) colloid transport is not significantly affected by varying the filtration parameters, (2) travel time to the water table decreases with the colloid size, (3) larger colloids show little retardation whereas very small ones are retarded significantly, and (4) fracture filtration can have an impact on transport. Because of uncertainties in the fundamentals of colloid transport and an extremely conservative approach (based on an improbably adverse worst-case scenario), caution should be exercised in the analysis and interpretation of the 3-D simulation results. The results discussed here should be viewed as an attempt to identify and evaluate the mechanisms, processes, and geological features that control colloidal transport

  7. pH Reversible Encapsulation of Oppositely Charged Colloids Mediated by Polyelectrolytes.

    Science.gov (United States)

    Guo, Yong; van Ravensteijn, Bas G P; Evers, Chris H J; Kegel, Willem K

    2017-05-09

    We report the first example of reversible encapsulation of micron-sized particles by oppositely charged submicron smaller colloids. The reversibility of this encapsulation process is regulated by pH-responsive poly(acrylic acid) (PAA) present in solution. The competitive adsorption between the small colloids and the poly(acrylic acid) on the surface of the large colloids plays a key role in the encapsulation behavior of the system. pH offers an experimental knob to tune the electrostatic interactions between the two oppositely charged particle species via regulation of the charge density of the poly(acrylic acid). This results in an increased surface coverage of the large colloids by the smaller colloids when decreasing pH. Furthermore, the poly(acrylic acid) also acts as a steric barrier limiting the strength of the attractive forces between the oppositely charged particle species, thereby enabling detachment of the smaller colloids. Finally, based on the pH tunability of the encapsulation behavior and the ability of the small colloids to detach, reversible encapsulation is achieved by cycling pH in the presence of the PAA polyelectrolytes. The role of polyelectrolytes revealed in this work provides a new and facile strategy to control heteroaggregation behavior between oppositely charged colloids, paving the way to prepare sophisticated hierarchical assemblies.

  8. Laboratory investigation of the role of desorption kinetics on americium transport associated with bentonite colloids.

    Science.gov (United States)

    Dittrich, Timothy Mark; Boukhalfa, Hakim; Ware, Stuart Douglas; Reimus, Paul William

    2015-10-01

    Understanding the parameters that control colloid-mediated transport of radionuclides is important for the safe disposal of used nuclear fuel. We report an experimental and reactive transport modeling examination of americium transport in a groundwater-bentonite-fracture fill material system. A series of batch sorption and column transport experiments were conducted to determine the role of desorption kinetics from bentonite colloids in the transport of americium through fracture materials. We used fracture fill material from a shear zone in altered granodiorite collected from the Grimsel Test Site (GTS) in Switzerland and colloidal suspensions generated from FEBEX bentonite, a potential repository backfill material. The colloidal suspension (100 mg L(-1)) was prepared in synthetic groundwater that matched the natural water chemistry at GTS and was spiked with 5.5 × 10(-10) M (241)Am. Batch characterizations indicated that 97% of the americium in the stock suspension was adsorbed to the colloids. Breakthrough experiments conducted by injecting the americium colloidal suspension through three identical columns in series, each with mean residence times of 6 h, show that more than 95% of the bentonite colloids were transported through each of the columns, with modeled colloid filtration rates (k(f)) of 0.01-0.02 h(-1). Am recoveries in each column were 55-60%, and Am desorption rate constants from the colloids, determined from 1-D transport modeling, were 0.96, 0.98, and 0.91 h(-1) in the three columns, respectively. The consistency in Am recoveries and desorption rate constants in each column indicates that the Am was not associated with binding sites of widely-varying strengths on the colloids, as one binding site with fast kinetics represented the system accurately for all three sequential columns. Our data suggest that colloid-mediated transport of Am in a bentonite-fracture fill material system is unlikely to result in transport over long distance scales because

  9. An expanded ostracod-based conductivity transfer function for climate reconstruction in the Levant

    Science.gov (United States)

    Mischke, Steffen; Almogi-Labin, Ahuva; Al-Saqarat, Bety; Rosenfeld, Arik; Elyashiv, Hadar; Boomer, Ian; Stein, Mordechai; Lev, Lilach; Ito, Emi

    2014-06-01

    We present the first modern calibration dataset linking ostracod assemblage composition to water chemistry, and other site-specific variables, in the hydrologically and geopolitically sensitive southern Levant region. A total of 42 ostracod taxa were recorded from the 178 sampled sites in Israel and Jordan. Ilyocypris spp., Heterocypris salina and Cypridopsis vidua are the most abundant taxa. Species strictly confined to freshwater conditions are Prionocypris zenkeri, Gomphocythere ortali and Prionocypris olivaceus. In contrast, H. salina, Bradleytriebella lineata and Cyprideis torosa show high frequencies in brackish waters (waters with higher conductivity). Humphcypris subterranea, G. ortali, P. olivaceus and Cypridopsis elongata apparently prefer flowing waters. Specific conductivity optima and tolerance ranges were calculated for the recorded ostracod species and may be used for the palaeoenvironmental assessment of fossil ostracod assemblages. In addition, a transfer-function for quantitative specific conductivity estimation based on 141 samples was established with weighted averaging partial least squares regression (WA-PLS). The resulting coefficient of determination r2 between observed and predicted conductivity values (0.72) and the root-mean-square error of prediction (RMSEP) in % gradient length (13.1) indicate that conductivity may be reliably estimated from ostracod assemblage data. The transfer function was first applied to last glacial ostracod assemblage data from an archaeological trench in the Sea of Galilee (northern Israel). Relatively large conductivity fluctuations between ca 1 and 7 mS cm-1 were inferred for the period 24-20 cal ka BP. In addition, four episodes of freshwater influx near the site of the trench were identified from the presence of shells of freshwater and stream-dwelling species intermingled with very abundant shells of Cyprideis torosa. The results of our study allow a better use of Quaternary ostracods from the Levant as

  10. Thermal conductivity measurements in soil using an instrument based on the cylindrical probe method

    Science.gov (United States)

    Nicolas, J.; André, Ph.; Rivez, JF.; Debbaut, V.

    1993-03-01

    The article discusses the underlying hypothesis, the limits, the range of application, and the practical operation of a versatile thermal conductivity analyzer based on a transient cylindrical probe method. The best expected precision for the conductivity determination appears to be ˜±10%. A compact analyzer, integrating all the apparatus' components in the same unit, has been specifically designed for environmental research in the field. Calibration received special attention regarding thermal conductivity values in the range 0.1-3 W/mK. The analyzer was tested on seven materials, in field conditions, and discrepancies from published conductivity values did not exceed 9%. Several checks were performed in the laboratory to study the influence of experimental conditions, such as the probe insertion technique. The cylindrical probe method appears well suited to powdered materials, but may also be applied to viscous liquids and solid matter. As an application, the cylindrical probe was used to characterize nine soils from the Belgian Lorraine. After soil analysis in the dry state, thermal conductivity of each sample was determined at different moisture contents. The transient cylindrical probe method proved to be quick and easy, whether in situ or on samples in the laboratory. It is a powerful tool which can map a country's soil thermal properties.

  11. Thermal conductivity model for powdered materials under vacuum based on experimental studies

    Directory of Open Access Journals (Sweden)

    N. Sakatani

    2017-01-01

    Full Text Available The thermal conductivity of powdered media is characteristically very low in vacuum, and is effectively dependent on many parameters of their constituent particles and packing structure. Understanding of the heat transfer mechanism within powder layers in vacuum and theoretical modeling of their thermal conductivity are of great importance for several scientific and engineering problems. In this paper, we report the results of systematic thermal conductivity measurements of powdered media of varied particle size, porosity, and temperature under vacuum using glass beads as a model material. Based on the obtained experimental data, we investigated the heat transfer mechanism in powdered media in detail, and constructed a new theoretical thermal conductivity model for the vacuum condition. This model enables an absolute thermal conductivity to be calculated for a powder with the input of a set of powder parameters including particle size, porosity, temperature, and compressional stress or gravity, and vice versa. Our model is expected to be a competent tool for several scientific and engineering fields of study related to powders, such as the thermal infrared observation of air-less planetary bodies, thermal evolution of planetesimals, and performance of thermal insulators and heat storage powders.

  12. Equivalence of the EMD- and NEMD-based decomposition of thermal conductivity into microscopic building blocks.

    Science.gov (United States)

    Matsubara, Hiroki; Kikugawa, Gota; Ishikiriyama, Mamoru; Yamashita, Seiji; Ohara, Taku

    2017-09-21

    Thermal conductivity of a material can be comprehended as being composed of microscopic building blocks relevant to the energy transfer due to a specific microscopic process or structure. The building block is called the partial thermal conductivity (PTC). The concept of PTC is essential to evaluate the contributions of various molecular mechanisms to heat conduction and has been providing detailed knowledge of the contribution. The PTC can be evaluated by equilibrium molecular dynamics (EMD) and non-equilibrium molecular dynamics (NEMD) in different manners: the EMD evaluation utilizes the autocorrelation of spontaneous heat fluxes in an equilibrium state whereas the NEMD one is based on stationary heat fluxes in a non-equilibrium state. However, it has not been fully discussed whether the two methods give the same PTC or not. In the present study, we formulate a Green-Kubo relation, which is necessary for EMD to calculate the PTCs equivalent to those by NEMD. Unlike the existing theories, our formulation is based on the local equilibrium hypothesis to describe a clear connection between EMD and NEMD simulations. The equivalence of the two derivations of PTCs is confirmed by the numerical results for liquid methane and butane. The present establishment of the EMD-NEMD correspondence makes the MD analysis of PTCs a robust way to clarify the microscopic origins of thermal conductivity.

  13. Equivalence of the EMD- and NEMD-based decomposition of thermal conductivity into microscopic building blocks

    Science.gov (United States)

    Matsubara, Hiroki; Kikugawa, Gota; Ishikiriyama, Mamoru; Yamashita, Seiji; Ohara, Taku

    2017-09-01

    Thermal conductivity of a material can be comprehended as being composed of microscopic building blocks relevant to the energy transfer due to a specific microscopic process or structure. The building block is called the partial thermal conductivity (PTC). The concept of PTC is essential to evaluate the contributions of various molecular mechanisms to heat conduction and has been providing detailed knowledge of the contribution. The PTC can be evaluated by equilibrium molecular dynamics (EMD) and non-equilibrium molecular dynamics (NEMD) in different manners: the EMD evaluation utilizes the autocorrelation of spontaneous heat fluxes in an equilibrium state whereas the NEMD one is based on stationary heat fluxes in a non-equilibrium state. However, it has not been fully discussed whether the two methods give the same PTC or not. In the present study, we formulate a Green-Kubo relation, which is necessary for EMD to calculate the PTCs equivalent to those by NEMD. Unlike the existing theories, our formulation is based on the local equilibrium hypothesis to describe a clear connection between EMD and NEMD simulations. The equivalence of the two derivations of PTCs is confirmed by the numerical results for liquid methane and butane. The present establishment of the EMD-NEMD correspondence makes the MD analysis of PTCs a robust way to clarify the microscopic origins of thermal conductivity.

  14. Conductivity Scaling Relationships in Nanostructured Membranes based on Protic Polymerized Ionic Liquids

    Science.gov (United States)

    Sanoja, Gabriel; Lynd, Nathaniel; Segalman, Rachel

    2015-03-01

    Nanostructured membranes based on protic polymerized ionic liquids are of great interest for a variety of electrochemical applications. Understanding the relationship between composition, structure, and ionic conductivity for these materials is essential for designing novel membranes with improved properties. In this work, we explore the effect of volume fraction of ionic liquid on conductivity, σ using a model system composed of poly[isoprene-block-(ethylene oxide-stat-histamine glycidyl ether) diblock copolymers [PI- b - P(EO-stat-HGE)] and the resulting [PI- b - P(EO-stat-IL)] obtained after treatment with trifluoroacetic acid. These materials self-assemble into lamellar structures with volume fractions of ionic liquid ranging from 0.50 to 0.90 as demonstrated by SAXS. PI- b - P(EO-stat-IL) membranes exhibit conductivities up to 4 x 10-3 S/cm at room temperature. In addition, PI- b - P(EO-stat-IL) based membranes have lower water uptake (λ = 8-10) in comparison with most proton conducting membranes reported elsewhere. The low λ in these membranes might translate into a stronger effect of morphology on transport properties. Joint Center for Artificial Photosynthesis.

  15. Evidence based administration of risperidone and paliperidone for the treating conduct disorder

    Directory of Open Access Journals (Sweden)

    Ahmad Ghanizadeh

    2013-01-01

    Full Text Available Background: This study evaluates the evidence-based administration of risperidone and paliperidone for the treating children and adolescents with conduct disorder (CD. Materials and Methods: A review of the current literature from clinical trials that investigated the efficacy of risperidone and paliperidone on CD considering the inclusion criteria and search strategies was performed by a search of PubMed and Google Scholar databases. Results: Out of 53 titles, 31 were irrelevant. The abstract of 22 potentially related articles were studied. Only six articles reported the results of clinical trial. However, one of them reported the effect of risperidone on conduct behaviors in autistic disorders. One study was a re-analysis of two previous studies, one study reported the effects of maintenance versus withdrawal of risperidone treatment and two studies included children with sub-average intelligence. Headache, somnolence and increased appetite are among the most common reported adverse effects. No study examined the effect of paliperidone on CD was found. Conclusion: Current literature suggests that risperidone could be effective for treating some conduct behaviors in children and adolescents. The effect of risperidone on CD is not a well-researched area. There is no well-controlled evidence based reports about the safety and efficacy of risperidone for the treatment of CD. Further trials should examine the efficacy of these medications on CD rather than conduct behaviors or disruptive behavior disorders.

  16. Morphology, molecular dynamics and electric conductivity of carbohydrate polymer films based on alginic acid and benzimidazole.

    Science.gov (United States)

    Rachocki, Adam; Pogorzelec-Glaser, Katarzyna; Pawlaczyk, Czesław; Tritt-Goc, Jadwiga

    2011-12-13

    The present paper describes a preparation method and molecular investigations of new biodegradable proton-conducting carbohydrate polymer films based on alginic acid and benzimidazole. Electric conductivity was studied in a wide temperature range in order to check the potential application of these compounds as membranes for electrochemical devices. Compared to pure alginic acid powder or its film, the biodegradable film of alginic acid with an addition of benzimidazole exhibits considerably higher conductivity in the range above water boiling temperature (up to approximately 10(-3) S/cm at 473 K). Due to this important feature the obtained films can be considered as candidates for application in high-temperature electrochemical devices. The microscopic nature and mechanism of the conduction in alginate based materials were studied by proton nuclear magnetic resonance (NMR). The results show specific changes in morphology and molecular dynamics between pure alginate powders and the films obtained without and with the addition of benzimidazole molecules. Copyright © 2011 Elsevier Ltd. All rights reserved.

  17. A highly sensitive, low-cost, wearable pressure sensor based on conductive hydrogel spheres

    KAUST Repository

    Tai, Yanlong

    2015-01-01

    Wearable pressure sensing solutions have promising future for practical applications in health monitoring and human/machine interfaces. Here, a highly sensitive, low-cost, wearable pressure sensor based on conductive single-walled carbon nanotube (SWCNT)/alginate hydrogel spheres is reported. Conductive and piezoresistive spheres are embedded between conductive electrodes (indium tin oxide-coated polyethylene terephthalate films) and subjected to environmental pressure. The detection mechanism is based on the piezoresistivity of the SWCNT/alginate conductive spheres and on the sphere-electrode contact. Step-by-step, we optimized the design parameters to maximize the sensitivity of the sensor. The optimized hydrogel sensor exhibited a satisfactory sensitivity (0.176 ΔR/R0/kPa-1) and a low detectable limit (10 Pa). Moreover, a brief response time (a few milliseconds) and successful repeatability were also demonstrated. Finally, the efficiency of this strategy was verified through a series of practical tests such as monitoring human wrist pulse, detecting throat muscle motion or identifying the location and the distribution of an external pressure using an array sensor (4 × 4). © 2015 The Royal Society of Chemistry.

  18. Properties of TiO{sub 2}-based transparent conducting oxides

    Energy Technology Data Exchange (ETDEWEB)

    Hitosugi, Taro [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 980-8577 Sendai (Japan); Yamada, Naoomi; Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Department of Chemistry, University of Tokyo, 113-0033 Tokyo (Japan)

    2010-07-15

    The development and properties of titanium dioxide (TiO{sub 2})-based transparent conducting oxides (TCO), which exhibit properties comparable to those of In{sub 2-x}Sn{sub x}O{sub 3} (ITO), are reviewed in this article. An epitaxial thin film of anatase Ti{sub 0.94}Nb{sub 0.06}O{sub 2} exhibited a resistivity ({rho}) of 2.3 x 10{sup -4}{omega} cm and internal transmittance of {proportional_to}95% in the visible light region. Furthermore, we prepared polycrystalline films with {rho} of 6.4 x 10{sup -4}{omega} cm at room temperature on glass substrates by using sputtering. We focus on characteristics unique to TiO{sub 2}-based TCO, such as a high refractive index, high transmittance in infrared, and high stability in reducing atmospheres. Possible applications of TiO{sub 2}-based TCOs, as well as the mechanism of the transparent conducting properties found in this d-electron-based TCO, are discussed in this review. Photograph showing TiO{sub 2}-based TCO on a transparent plastic film. Note that the film appears greenish due to interference in the film originating from its high refractive index. This high refractive index is one of the unique characteristics of TiO{sub 2}-based TCO. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  19. Design of a smart ECG garment based on conductive textile electrode and flexible printed circuit board.

    Science.gov (United States)

    Cai, Zhipeng; Luo, Kan; Liu, Chengyu; Li, Jianqing

    2017-08-09

    A smart electrocardiogram (ECG) garment system was designed for continuous, non-invasive and comfortable ECG monitoring, which mainly consists of four components: Conductive textile electrode, garment, flexible printed circuit board (FPCB)-based ECG processing module and android application program. Conductive textile electrode and FPCB-based ECG processing module (6.8 g, 55 mm × 53 mm × 5 mm) are identified as two key techniques to improve the system's comfort and flexibility. Preliminary experimental results verified that the textile electrodes with circle shape, 40 mm size in diameter, and 5 mm thickness sponge are best suited for the long-term ECG monitoring application. The tests on the whole system confirmed that the designed smart garment can obtain long-term ECG recordings with high signal quality.

  20. Transparent conductive graphene electrode in GaN-based ultra-violet light emitting diodes.

    Science.gov (United States)

    Kim, Byung-Jae; Mastro, Michael A; Hite, Jennifer; Eddy, Charles R; Kim, Jihyun

    2010-10-25

    We report a graphene-based transparent conductive electrode for use in ultraviolet (UV) GaN light emitting diodes (LEDs). A few-layer graphene (FLG) layer was mechanically deposited. UV light at a peak wavelength of 368 nm was successfully emitted by the FLG layer as transparent contact to p-GaN. The emission of UV light through the thin graphene layer was brighter than through the thick graphene layer. The thickness of the graphene layer was characterized by micro-Raman spectroscopy. Our results indicate that this novel graphene-based transparent conductive electrode holds great promise for use in UV optoelectronics for which conventional ITO is less transparent than graphene.

  1. Conducting polymer and its composite materials based electrochemical sensor for Nicotinamide Adenine Dinucleotide (NADH).

    Science.gov (United States)

    Omar, Fatin Saiha; Duraisamy, Navaneethan; Ramesh, K; Ramesh, S

    2016-05-15

    Nicotinamide Adenine Dinucleotide (NADH) is an important coenzyme in the human body that participates in many metabolic reactions. The impact of abnormal concentrations of NADH significantly causes different diseases in human body. Electrochemical detection of NADH using bare electrode is a challenging task especially in the presence of main electroactive interferences such as ascorbic acid (AA), uric acid (UA) and dopamine (DA). Modified electrodes have been widely explored to overcome the problems of poor sensitivity and selectivity occurred from bare electrodes. This review gives an overview on the progress of using conducting polymers, polyelectrolyte and its composites (co-polymer, carbonaceous, metal, metal oxide and clay) based modified electrodes for the sensing of NADH. In addition, developments on the fabrication of numerous conducting polymer composites based modified electrodes are clearly described. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Cholesteric colloidal liquid crystals from phytosterol rod-like particles

    NARCIS (Netherlands)

    Rossi, L.; Sacanna, S.; Velikov, K.P.

    2011-01-01

    We report the first observation of chiral colloidal liquid crystals of rod-like particles from a low molecular weight organic compound— phytosterols. Based on the particles shape and crystal structure, we attribute this phenomenon to chiral distribution of surface charge on the surface of

  3. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    International Nuclear Information System (INIS)

    Liu, Haitao

    2007-01-01

    In the last two decades, the field of nanoscience and nanotechnology has witnessed tremendous advancement in the synthesis and application of group II-VI colloidal nanocrystals. The synthesis based on high temperature decomposition of organometallic precursors has become one of the most successful methods of making group II-VI colloidal nanocrystals. This method is first demonstrated by Bawendi and coworkers in 1993 to prepare cadmium chalcogenide colloidal quantum dots and later extended by others to prepare other group II-VI quantum dots as well as anisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod. This dissertation focuses on the chemistry of this type of nanocrystal synthesis. The synthesis of group II-VI nanocrystals was studied by characterizing the molecular structures of the precursors and products and following their time evolution in the synthesis. Based on these results, a mechanism was proposed to account for the 2 reaction between the precursors that presumably produces monomer for the growth of nanocrystals. Theoretical study based on density functional theory calculations revealed the detailed free energy landscape of the precursor decomposition and monomer formation pathway. Based on the proposed reaction mechanism, a new synthetic method was designed that uses water as a novel reagent to control the diameter and the aspect ratio of CdSe and CdS nanorods

  4. Population Balance Modeling of Aggregation and Coalescence in Colloidal Systems

    NARCIS (Netherlands)

    Kryven, I.; Lazzari, S.; Storti, G.

    2014-01-01

    A complex interplay between aggregation and coalescence occurs in many colloidal polymeric systems and determines the morphology of the final clusters of primary particles. To describe this process, a 2D population balance equation (PBE) based on cluster mass and fractal dimension is solved,

  5. The Design of a Novel Flexible Tactile Sensor Based on Pressure-conductive Rubber

    Directory of Open Access Journals (Sweden)

    Fei Xu

    2011-01-01

    Full Text Available A novel flexible tactile sensor using conductive rubber with electrical-wires knitted method is presented. The sensor’s design is based on rubber’s pressure-sensitive property. It is flexible and can be mounted on any object to measure tactile information. The mathematic piezoresistivity model of the rubber is described, and we also discuss the sensor’s structure and scanning method. The simulation results show that the sensor can detect pressure accurately.

  6. What happens when pharmaceuticals meet colloids.

    Science.gov (United States)

    Xing, Yingna; Chen, Xijuan; Zhuang, Jie; Chen, Xin

    2015-12-01

    Pharmaceuticals (PCs) have been widely detected in natural environment due to agricultural application of reclaimed water, sludge and animal wastes. Their potential risks to various ecosystems and even to human health have caused great concern; however, little was known about their environmental behaviors. Colloids (such as clays, metal oxides, and particulate organics) are kind of substances that are active and widespread in the environment. When PCs meet colloids, their interaction may influence the fate, transport, and toxicity of PCs. This review summarizes the progress of studies on the role of colloids in mediating the environmental behaviors of PCs. Synthesized results showed that colloids can adsorb PCs mainly through ion exchange, complexation and non-electrostatic interactions. During this process the structure of colloids and the stability of PCs may be changed. The adsorbed PCs may have higher risks to induce antibiotic resistance; besides, their transport may also be altered considering they have great chance to move with colloids. Solution conditions (such as pH, ionic strength, and cations) could influence these interactions between PCs and colloids, as they can change the forms of PCs and alter the primary forces between PCs and colloids in the solution. It could be concluded that PCs in natural soils could bind with colloids and then co-transport during the processes of irrigation, leaching, and erosion. Therefore, colloid-PC interactions need to be understood for risk assessment of PCs and the best management practices of various ecosystems (such as agricultural and wetland systems).

  7. Conducting Internet-based HIV/STD prevention survey research: considerations in design and evaluation.

    Science.gov (United States)

    Pequegnat, Willo; Rosser, B R Simon; Bowen, Anne M; Bull, Sheana S; DiClemente, Ralph J; Bockting, Walter O; Elford, Jonathan; Fishbein, Martin; Gurak, Laura; Horvath, Keith; Konstan, Joseph; Noar, Seth M; Ross, Michael W; Sherr, Lorraine; Spiegel, David; Zimmerman, Rick

    2007-07-01

    The aim of this paper is to advance rigorous Internet-based HIV/STD Prevention quantitative research by providing guidance to fellow researchers, faculty supervising graduates, human subjects' committees, and review groups about some of the most common and challenging questions about Internet-based HIV prevention quantitative research. The authors represent several research groups who have gained experience conducting some of the first Internet-based HIV/STD prevention quantitative surveys in the US and elsewhere. Sixteen questions specific to Internet-based HIV prevention survey research are identified. To aid rigorous development and review of applications, these questions are organized around six common criteria used in federal review groups in the US: significance, innovation, approach (broken down further by research design, formative development, procedures, sampling considerations, and data collection); investigator, environment and human subjects' issues. Strategies promoting minority participant recruitment, minimizing attrition, validating participants, and compensating participants are discussed. Throughout, the implications on budget and realistic timetabling are identified.

  8. A hot-wire method based thermal conductivity measurement apparatus for teaching purposes

    Science.gov (United States)

    Alvarado, S.; Marín, E.; Juárez, A. G.; Calderón, A.; Ivanov, R.

    2012-07-01

    The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer and a high purity platinum wire). The wire, which is immersed in the investigated sample, is heated by passing a constant electrical current through it, and its temperature evolution, ΔT, is measured as a function of time, t, for several values of the current. A straightforward methodology is then used for data processing in order to obtain the liquid thermal conductivity. The start point is the well known linear relationship between ΔT and ln(t) predicted for long heating times by a model based on a solution of the heat conduction equation for an infinite lineal heat source embedded in an infinite medium into which heat is conducted without convective and radiative heat losses. A criterion is used to verify that the selected linear region is the one that matches the conditions imposed by the theoretical model. As a consequence the method involves least-squares fits in linear, semi-logarithmic (semi-log) and log-log graphs, so that it becomes attractive not only to teach about heat transfer and thermal properties measurement techniques, but also as a good exercise for students of undergraduate courses of physics and engineering learning about these kinds of mathematical functional relationships between variables. The functionality of the experiment was demonstrated by measuring the thermal conductivity in samples of liquids with well known thermal properties.

  9. A hot-wire method based thermal conductivity measurement apparatus for teaching purposes

    International Nuclear Information System (INIS)

    Alvarado, S; Marín, E; Juárez, A G; Calderón, A; Ivanov, R

    2012-01-01

    The implementation of an automated system based on the hot-wire technique is described for the measurement of the thermal conductivity of liquids using equipment easily available in modern physics laboratories at high schools and universities (basically a precision current source and a voltage meter, a data acquisition card, a personal computer and a high purity platinum wire). The wire, which is immersed in the investigated sample, is heated by passing a constant electrical current through it, and its temperature evolution, ΔT, is measured as a function of time, t, for several values of the current. A straightforward methodology is then used for data processing in order to obtain the liquid thermal conductivity. The start point is the well known linear relationship between ΔT and ln(t) predicted for long heating times by a model based on a solution of the heat conduction equation for an infinite lineal heat source embedded in an infinite medium into which heat is conducted without convective and radiative heat losses. A criterion is used to verify that the selected linear region is the one that matches the conditions imposed by the theoretical model. As a consequence the method involves least-squares fits in linear, semi-logarithmic (semi-log) and log-log graphs, so that it becomes attractive not only to teach about heat transfer and thermal properties measurement techniques, but also as a good exercise for students of undergraduate courses of physics and engineering learning about these kinds of mathematical functional relationships between variables. The functionality of the experiment was demonstrated by measuring the thermal conductivity in samples of liquids with well known thermal properties. (paper)

  10. Isothermal titration calorimetric studies of the acid-base properties of poly(N-isopropylacrylamide-co-4-vinylpyridine) cationic polyelectrolyte colloidal microgels

    International Nuclear Information System (INIS)

    Seidel, J.; Pinkrah, V.T.; Mitchell, J.C.; Chowdhry, B.Z.; Snowden, M.J.

    2004-01-01

    Isothermal titration calorimetry (ITC) and potentiometric titration were used to study the protonation properties of the 4-vinylpyridine (4-VP) moiety in cationic poly(N-isopropylacrylamide-co-4-vinylpyridine) colloidal microgels [poly(NIPAM-co-4-VP)]. Calorimetric pH titrations were performed using microgels of different 4-VP content and the influence of ionic strength and counter ions have been examined. The calorimetric titration output consists of several thermal contributions reflecting the complex nature of the interactions in the aqueous microgel dispersions. In contrast to the potentiometric results, the calorimetric titration data could not be completely described by a theoretical model solely taking into account protonation equilibria. Deviations from the proposed model correlate with swelling or shrinking of the gel particles. The calorimetric results also reveal a pronounced counter-ion effect of perchlorate compared to chloride ions. In the presence of perchlorate ions, small secondary thermal effects accompany protonation of the 4-VP moiety due, in part, to kinetically limited conformational changes in the co-polymer microgel

  11. Scintigraphic study of gastric emptying with colloidal tin

    International Nuclear Information System (INIS)

    Rodríguez Paleo, Lester; Nuez Vilar, Maricela; Machado Lois, Marisel; López González, María Karla; Torres Leyva, Oscar; Izquierdo Izquierdo, Yimel; García González, Idelsy; Conesa Gonzalez, Ana Ibis

    2016-01-01

    Gastroparesis is defined as a delay in gastric emptying in the absence of mechanical obstruction, associated with symptoms such as nausea and / or vomiting, feeling of postprandial gastric fullness, early satiety or epigastric pain for more than 3 months. The gold standard in the diagnosis of delayed gastric emptying scintigraphy is gastric emptying and radiopharmaceutical has been used more 99m Tc-sulfur colloid not available in the country. In order to evaluate the usefulness of colloidal tin in the scintigraphic gastric emptying study, a descriptive study was conducted in 64 patients over 18 years using as radiopharmaceutical 99m Tc-Sn colloid. 31% of patients had symptoms. The emptying time was normal in 50 cases and the association of gastroparesis symptoms was observed in 20 (15 diabetic and 5 non-diabetic), 9 patients had a delayed emptying, but reported no symptoms. Gastroparesis was more frequent in women than in men (35% versus 21%). 21% of patients had a moderate delayed gastric emptying. Conclusions: The results obtained with 99m Tc-Sn colloid are comparable to those reported by other authors using 99m Tc-SC in the scintigraphic assessment of gastric emptying. (author)

  12. Physics of Colloids in Space (PCS) Flight Hardware Developed

    Science.gov (United States)

    Koudelka, John M.

    2001-01-01

    investigation that will be located in an Expedite the Process of Experiments to Space Station (EXPRESS) Rack. The investigation will be conducted in the International Space Station U.S. laboratory, Destiny, over a period of approximately 10 months during the station assembly period from flight 6A through flight UF-2. This experiment will gather data on the basic physical properties of colloids by studying three different colloid systems with the objective of understanding how they grow and what structures they form. A colloidal suspension consists of fine particles (micrometer to submicrometer) suspended in a fluid for example, paints, milk, salad dressings, and aerosols. The long-term goal of this investigation is to learn how to steer the growth of colloidal suspensions to create new materials and new structures. This experiment is part of a two-stage investigation conceived by Professor David Weitz of Harvard University along with Professor Peter Pusey of the University of Edinburgh. The experiment hardware was developed by the NASA Glenn Research Center through contracts with Dynacs, Inc., and ZIN Technologies.

  13. Thermal conductivity studies of novel nanofluids based on metallic silver decorated mesoporous silica nanoparticles

    International Nuclear Information System (INIS)

    Tadjarodi, Azadeh; Zabihi, Fatemeh

    2013-01-01

    Graphical abstract: - Highlights: • Metallic silver was decorated in mSiO 2 with grafted hemiaminal functional groups. • Synthesized nanoparticles were used for preparation of glycerol based nanofluids. • The effect of temperature, weight fraction of mSiO 2 and concentration of silver nanoparticles on thermal conductivity of nanofluids was investigated. - Abstract: In the present study, the mesoporous structure of silica (mSiO 2 ) nanoparticles as well as hemiaminal grafted mSiO 2 decorated by metallic silver (Ag/mSiO 2 ) has been used for the preparation of glycerol based nanofluids. Structural and morphological characterization of the synthesized products have been carried out using Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), UV–vis spectroscopy, inductively coupled plasma (ICP) and N 2 adsorption–desorption isotherms. The thermal conductivity and viscosity of the nanofluids have been measured as a function of temperature for various weight fractions and silver concentrations of mSiO 2 and Ag/mSiO 2 nanoparticles, respectively. The results show that the thermal conductivity of the nanofluids increase up to 9.24% as the weight fraction of mSiO 2 increases up to 4 wt%. Also, increasing the percent of the silver decorated mSiO 2 (Ag/mSiO 2 ) up to 2.98% caused an enhancement in the thermal conductivity of the base fluid up to 10.95%. Furthermore, the results show that the nanofluids have Newtonian behavior in the tested temperature range for various concentrations of nanoparticles

  14. A simplistic analytical unit cell based model for the effective thermal conductivity of high porosity open-cell metal foams

    International Nuclear Information System (INIS)

    Yang, X H; Kuang, J J; Lu, T J; Han, F S; Kim, T

    2013-01-01

    We present a simplistic yet accurate analytical model for the effective thermal conductivity of high porosity open-cell metal foams saturated in a low conducting fluid (air). The model is derived analytically based on a realistic representative unit cell (a tetrakaidecahedron) under the assumption of one-dimensional heat conduction along highly tortuous-conducting ligaments at high porosity ranges (ε ⩾ 0.9). Good agreement with existing experimental data suggests that heat conduction along highly conducting and tortuous ligaments predominantly defines the effective thermal conductivity of open-cell metal foams with negligible conduction in parallel through the fluid phase. (paper)

  15. Definition of management zones in coffee production fields based on apparent soil electrical conductivity

    Directory of Open Access Journals (Sweden)

    Domingos Sárvio Magalhães Valente

    2012-06-01

    Full Text Available Fertilizer application at variable rates requires dense sampling to determine the resulting field spatial variability. Defining management zones is a technique that facilitates the variable-rate application of agricultural inputs. The apparent electrical conductivity of the soil is an important factor in explaining the variability of soil physical-chemical properties. Thus, the objective of this study was to define management zones for coffee (Coffea Arabica L. production fields based on spatial variability of the apparent electrical conductivity of the soil. The resistivity method was used to measure the apparent soil electrical conductivity. Soil samples were collected to measure the chemical and physical soil properties. The maps of spatial variability were generated using ordinary kriging method. The fuzzy k-means algorithm was used to delimit the management zones. To analyze the agreement between the management zones and the soil properties, the kappa coefficients were calculated. The best results were obtained for the management zones defined using the apparent electrical conductivity of the soil and the digital elevation model. In this case, the kappa coefficient was 0.45 for potassium, which is an element that is associated with quality coffee. The other variable that had a high kappa coefficient was remaining phosphorous; the coefficient obtained was 0.49. The remaining phosphorus is an important parameter for determining which fertilizers and soil types to study.

  16. Thermal conductivity enhancement of nano-silver particles dispersed ethylene glycol based nanofluids

    Science.gov (United States)

    Khamliche, Touria; Khamlich, Saleh; Doyle, Terry B.; Makinde, Daniel; Maaza, Malik

    2018-03-01

    This contribution reports on the thermal conductivity enhancement of nano-silver particles (nAgPs) based nanofluids with various nAgPs’ shapes in view of their potential application in concentrated solar power systems. More accurately, the thermal conductivity behaviour of suspensions of nAgPs dispersed ethylene glycol (nAgPs:EG), prepared by a simple and cost effective chemical synthesis method, is compared with a theoretical prediction. The effect of aging time on the shape of the dispersed nAgPs was clearly observed by the structural, optical and morphological analysis. Spherically shaped and Ag nanowires (AgNWs) with high yields were observed when the nAgPs was aged for 1 and 5 h, respectively. The observed AgNWs showed high aspect ratio (≥200) when EG and polyvinylpyrrolidone (PVP) were used as reductant and structure-directing agents. The thermal conductivity measurements on nAgPs:EG nanofuids with different volume fractions of nAgPs were conducted in a temperature range 25 generally monotonic increase with temperature and an approximately linear relationship with the volume fraction of the nAgPs. Particularly, an enhancement of up to 23% was observed when the nanofluid was aged for 5 h and AgNWs were dominant.

  17. Transport and dielectric studies on silver based molybdo-tungstate quaternary superionic conducting glasses

    International Nuclear Information System (INIS)

    Prasad, P.S.S.; Radhakrishna, S.

    1988-01-01

    The molybdo-tungstate (MoO 3 -WO 3 ) combination of glass formers with silver oxide (Ag 2 O) as glass modifier and silver iodide (AgI) as ionic conductor were prepared to study the transport and dielectric properties of 60% AgI-40% (x Ag 2 O-y(WO 3 -MoO 3 )) for x/y=0.33 to 3.0 and establish the feasibility of using these glasses as electrolytes in the fabrication and characterisation of solid state batteries and potential memory devices. The details of the preparation of glasses and methods of measurement of their capacitance, dielectric loss factor and ac conductivity in the frequency range 100 Hz - 100 kHz from 30-120 C have been reported. The electronic contribution to the total conductivity, the ionic and electronic transport numbers were determined using Wagners dc polarisation technique. The observed high ionic and low electronic conductivities were attributed to the formation of ionic clusters in the glass and the effect of mixing two glass formers. The observed total ionic conductivity and its temperature dependence was explained using Arrhenius relation σ=σ 0 /T exp(-E/RT) and the measured dielectric constant and dielectric loss were explained on the basis of Jonschers theory. The frequency dependence of dielectric constant obeys the theory based on the polarisation of ions. 25 refs.; 8 figs

  18. Electrical conductivity of the crust in central Baja California, México, based on magnetotelluric observations

    Science.gov (United States)

    Romo, J. M.; Gómez-Treviño, E.; Flores-Luna, C.; García-Abdeslem, J.

    2017-12-01

    Crustal and sub-crustal structure of northwestern Mexico (peninsular California) resulted from major accretion episodes occurred during the long-lived subduction of the Farallon plate beneath the North American plate, since late Jurassic time. A magnetotelluric profile across central Baja California reveals several electrical conductivity anomalies probably associated to the crustal boundaries of distinct Mezosoic terranes juxtaposed in the current peninsular crust. It is known that electrical conductivity is significantly increased by the pervasive presence of conductive minerals generated during metamorphic processes in highly sheared zones. We interpret a striking sub-horizontal conductivity anomaly reveled in the model as explained by the presence of high-salinity fluids released after dehydration of the subducted Magdalena microplate (Farallon plate?). The presence of fluids at the base of the peninsular crust may produce a zone of weakness, which supports the idea that Baja California lithosphere has not been entirely coupled to the Pacific plate. In addition, crustal thickness is estimated in our model in about 35 km beneath the western Peninsular Ranges batholith (PRB) and 20 km beneath the eastern PRB. This crustal thickness is in good agreement with independent estimations of a thinner crust in the Gulf of California margin and a thicker crust along the axial PRB.

  19. 3D printable highly conductive and mechanically strong thermoplastic-based nanocomposites

    Science.gov (United States)

    Tabiai, Ilyass; Therriault, Daniel

    Highly conductive 3D printable inks can be used to design electrical devices with various functionalities and geometries. We use the solvent evaporation assisted 3D-printing method to create high resolution structures made of poly(lactid) acid (PLA) reinforced with multi-walled carbon nanotube (MWCNTs). We characterize fibers with diameters ranging between 100 μm to 330 μm and reinforced with MWCNTs from 0.5 up to 40wt% here. Tensile test, shrinkage ratio, density and electrical conductivity measurements of the printed nanocomposite are presented. The material's electrical conductivity is strongly improved by adding MWCNTs (up to 3000S/m), this value was found to be higher than any 3D-printable carbon based material available in the literature. It is observed that MWCNTs significantly increase the material's strength and stiffness while reducing its ductility. The ink's density was also higher while still being in the range of polymers' densities. The presented nanocomposite is light weight, highly conductive, has good mechanical properties and can be printed in a freeform fashion at the micro scale. A myriad of low power consumption with less resistive heating sensors and devices can potentially be designed using it and integrated into other 3D printable products.

  20. Colloidal Quantum Dot Photovoltaics: A Path Forward

    KAUST Repository

    Kramer, Illan J.

    2011-11-22

    Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of specific wavelengths from across the sun\\'s broad spectrum. CQD materials\\' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements represent important first steps toward commercially compelling performance. Here we review advances in device architecture and materials science. We diagnose the principal phenomenon-electronic states within the CQD film band gap that limit both current and voltage in devices-that must be cured for CQD PV devices to fulfill their promise. We close with a prescription, expressed as bounds on the density and energy of electronic states within the CQD film band gap, that should allow device efficiencies to rise to those required for the future of the solar energy field. © 2011 American Chemical Society.

  1. Movie of phase separation during physics of colloids in space experiment

    Science.gov (United States)

    2002-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area in the video is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  2. Phase separation during the Experiment on Physics of Colloids in Space

    Science.gov (United States)

    2003-01-01

    Still photographs taken over 16 hours on Nov. 13, 2001, on the International Space Station have been condensed into a few seconds to show the de-mixing -- or phase separation -- process studied by the Experiment on Physics of Colloids in Space. Commanded from the ground, dozens of similar tests have been conducted since the experiment arrived on ISS in 2000. The sample is a mix of polymethylmethacrylate (PMMA or acrylic) colloids, polystyrene polymers and solvents. The circular area is 2 cm (0.8 in.) in diameter. The phase separation process occurs spontaneously after the sample is mechanically mixed. The evolving lighter regions are rich in colloid and have the structure of a liquid. The dark regions are poor in colloids and have the structure of a gas. This behavior carnot be observed on Earth because gravity causes the particles to fall out of solution faster than the phase separation can occur. While similar to a gas-liquid phase transition, the growth rate observed in this test is different from any atomic gas-liquid or liquid-liquid phase transition ever measured experimentally. Ultimately, the sample separates into colloid-poor and colloid-rich areas, just as oil and vinegar separate. The fundamental science of de-mixing in this colloid-polymer sample is the same found in the annealing of metal alloys and plastic polymer blends. Improving the understanding of this process may lead to improving processing of these materials on Earth.

  3. Spontaneous Detachment of Colloids from Primary Energy Minima by Brownian Diffusion.

    Directory of Open Access Journals (Sweden)

    Zhan Wang

    Full Text Available The Derjaguin-Landau-Verwey-Overbeek (DLVO interaction energy profile has been frequently used to interpret the mechanisms controlling colloid attachment/detachment and aggregation/disaggregation behavior. This study highlighted a type of energy profile that is characterized by a shallow primary energy well (i.e., comparable to the average kinetic energy of a colloid at a small separation distance and a monotonic decrease of interaction energy with separation distance beyond the primary energy well. This energy profile is present due to variations of height, curvature, and density of discrete physical heterogeneities on collector surfaces. The energy profile indicates that colloids can be spontaneously detached from the shallow primary energy well by Brownian diffusion. The spontaneous detachment from primary minima was unambiguously confirmed by conducting laboratory column transport experiments involving flow interruptions for two model colloids (polystyrene latex microspheres and engineered nanoparticles (fullerene C60 aggregates. Whereas the spontaneous detachment has been frequently attributed to attachment in secondary minima in the literature, our study indicates that the detached colloids could be initially attached at primary minima. Our study further suggests that the spontaneous disaggregation from primary minima is more significant than spontaneous detachment because the primary minimum depth between colloid themselves is lower than that between a colloid and a collector surface.

  4. Spontaneous Detachment of Colloids from Primary Energy Minima by Brownian Diffusion.

    Science.gov (United States)

    Wang, Zhan; Jin, Yan; Shen, Chongyang; Li, Tiantian; Huang, Yuanfang; Li, Baoguo

    2016-01-01

    The Derjaguin-Landau-Verwey-Overbeek (DLVO) interaction energy profile has been frequently used to interpret the mechanisms controlling colloid attachment/detachment and aggregation/disaggregation behavior. This study highlighted a type of energy profile that is characterized by a shallow primary energy well (i.e., comparable to the average kinetic energy of a colloid) at a small separation distance and a monotonic decrease of interaction energy with separation distance beyond the primary energy well. This energy profile is present due to variations of height, curvature, and density of discrete physical heterogeneities on collector surfaces. The energy profile indicates that colloids can be spontaneously detached from the shallow primary energy well by Brownian diffusion. The spontaneous detachment from primary minima was unambiguously confirmed by conducting laboratory column transport experiments involving flow interruptions for two model colloids (polystyrene latex microspheres) and engineered nanoparticles (fullerene C60 aggregates). Whereas the spontaneous detachment has been frequently attributed to attachment in secondary minima in the literature, our study indicates that the detached colloids could be initially attached at primary minima. Our study further suggests that the spontaneous disaggregation from primary minima is more significant than spontaneous detachment because the primary minimum depth between colloid themselves is lower than that between a colloid and a collector surface.

  5. Colloid-Facilitated Transport of Cations in an Unsaturated Fractured Soil Under Transient Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Ryan, Joseph [Univ. of Colorado, Boulder, CO (United States)

    2015-01-31

    Rainfall experiments were conducted using intact soil cores and an instrumented soil pedon to examine the effect of physical heterogeneity and rainfall characteristics on the mobilization of colloids, organic matter, cesium, and strontium in a fractured soil. To measure the spatial variability of infiltration of colloids and contaminants, samples were collected through a 19-port grid placed below the soil core in laboratory study and in 27 samplers at multiple depths in the soil pedon in the field study. Cesium and strontium were applied to the soil cores and the soil pedon prior to mobilization experiments. Rainwater solutions of multiple ionic strengths and organic matter concentrations were applied to the soil cores and soil pedon to mobilize in situ colloids, cesium, and strontium. The mobilization of colloids and metal cations occurred through preferential flow paths in the soil cores. Compared to steady rainfall, greater amounts of colloids were mobilized during rainfall interrupted by pauses, which indicates that the supply of colloids to be mobilized was replenished during the pauses. A maximum in the amount of mobilized colloids were mobilized during a rainfall following a pause of 2.5 d. Pauses of shorter or longer duration resulted in less colloid mobilization. Freeze-thaw cycles, a transient condition in winter, enhanced colloid mobilization and colloid-facilitated transport of cesium and strontium in the soil cores. The exchange of solutes between the soil matrix and macropores caused a hysteretic mobilization of colloids, cesium, and strontium during changes in ionic strength. Colloid-facilitated mobilization of cesium and strontium was important at low ionic strength in fractures where slow flow allowed greater exchange of flow between the fractures and the surrounding matrix. The release of cesium and strontium by cation exchange occurred at high ionic strength in fractures where there is a little exchange of pore water with the surrounding matrix

  6. Glass transition of soft colloids

    Science.gov (United States)

    Philippe, Adrian-Marie; Truzzolillo, Domenico; Galvan-Myoshi, Julian; Dieudonné-George, Philippe; Trappe, Véronique; Berthier, Ludovic; Cipelletti, Luca

    2018-04-01

    We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τα of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τα on approaching the glass transition is independent of particle softness. By contrast, softness becomes relevant at very large packing fractions when the system falls out of equilibrium. In this nonequilibrium regime, τα depends surprisingly weakly on packing fraction, and time correlation functions exhibit a compressed exponential decay consistent with stress-driven relaxation. The transition to this novel regime coincides with the onset of an anomalous decrease in local order with increasing density typical of ultrasoft systems. We propose that these peculiar dynamics results from the combination of the nonequilibrium aging dynamics expected in the glassy state and the tendency of colloids interacting through soft potentials to refluidize at high packing fractions.

  7. Conducting Polymer-Based Nanohybrid Transducers: A Potential Route to High Sensitivity and Selectivity Sensors

    Directory of Open Access Journals (Sweden)

    Seon Joo Park

    2014-02-01

    Full Text Available The development of novel sensing materials provides good opportunities to realize previously unachievable sensor performance. In this review, conducting polymer-based nanohybrids are highlighted as innovative transducers for high-performance chemical and biological sensing devices. Synthetic strategies of the nanohybrids are categorized into four groups: (1 impregnation, followed by reduction; (2 concurrent redox reactions; (3 electrochemical deposition; (4 seeding approach. Nanocale hybridization of conducting polymers with inorganic components can lead to improved sorption, catalytic reaction and/or transport behavior of the material systems. The nanohybrids have thus been used to detect nerve agents, toxic gases, volatile organic compounds, glucose, dopamine, and DNA. Given further advances in nanohybrids synthesis, it is expected that sensor technology will also evolve, especially in terms of sensitivity and selectivity.

  8. Conductive Microporous Covalent Triazine-Based Framework for High-Performance Electrochemical Capacitive Energy Storage.

    Science.gov (United States)

    Li, Yajuan; Zheng, Shuanghao; Liu, Xue; Li, Pan; Sun, Lei; Yang, Ruixia; Wang, Sen; Wu, Zhong-Shuai; Bao, Xinhe; Deng, Wei-Qiao

    2017-11-14

    Nitrogen-enriched porous nanocarbon, graphene, and conductive polymers attract increasing attention for application in supercapacitors. However, electrode materials with a large specific surface area (SSA) and a high nitrogen doping concentration, which is needed for excellent supercapacitors, has not been achieved thus far. Herein, we developed a class of tetracyanoquinodimethane-derived conductive microporous covalent triazine-based frameworks (TCNQ-CTFs) with both high nitrogen content (>8 %) and large SSA (>3600 m 2  g -1 ). These CTFs exhibited excellent specific capacitances with the highest value exceeding 380 F g -1 , considerable energy density of 42.8 Wh kg -1 , and remarkable cycling stability without any capacitance degradation after 10 000 cycles. This class of CTFs should hold a great potential as high-performance electrode material for electrochemical energy-storage systems. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. A PC-based Technique to Measure the Thermal Conductivity of Solid Materials

    Directory of Open Access Journals (Sweden)

    ALETY Sridevireddy

    2009-01-01

    Full Text Available A PC-based technique to measure the thermal conductivity of a bulk material using steady-state one-dimensional heat flow technique is developed. The system uses a small metal rod as a sample and PT100 RTD sensors for temperature measurement. The output of the sensor is signaling conditioned and linearised using a special analog hardware. This linearised RTD output is fed to the analog input of the ADC through a multiplexer, which is interfaced to an IBM compatible PC through digital I/O card. A special constant current source circuit is designed for heating the sample. Software is developed in C-language. Thermal conductivity of two samples (Copper and Aluminum was measured.

  10. Effect of recent popularity on heat-conduction based recommendation models

    Science.gov (United States)

    Li, Wen-Jun; Dong, Qiang; Shi, Yang-Bo; Fu, Yan; He, Jia-Lin

    2017-05-01

    Accuracy and diversity are two important measures in evaluating the performance of recommender systems. It has been demonstrated that the recommendation model inspired by the heat conduction process has high diversity yet low accuracy. Many variants have been introduced to improve the accuracy while keeping high diversity, most of which regard the current node-degree of an item as its popularity. However in this way, a few outdated items of large degree may be recommended to an enormous number of users. In this paper, we take the recent popularity (recently increased item degrees) into account in the heat-conduction based methods, and propose accordingly the improved recommendation models. Experimental results on two benchmark data sets show that the accuracy can be largely improved while keeping the high diversity compared with the original models.

  11. Colloidal transparent conducting oxide nanocrystals: A new infrared ...

    Indian Academy of Sciences (India)

    2015-06-02

    Jun 2, 2015 ... the nanocrystal surface and (ii) carrier localization in the case of NCs having diame- ters less than the ... refers to an oxygen atom present on an oxygen site with a neutral charge on the defect site. On the other hand, ... represents an oxygen atom present at an interstitial position leaving a. −2 charge at the ...

  12. Colloidal transparent conducting oxide nanocrystals: A new infrared ...

    Indian Academy of Sciences (India)

    2015-06-02

    Jun 2, 2015 ... ture because the free electrons generated after Sn doping screen the Coulomb interaction between the .... sion of quantum mechanical treatment too which was provided by the Lorentz oscillator model [20]. ..... Magnetic response provides contrast in magnetic resonance imaging (MRI) to identify and locate.

  13. Preparation of radioactive colloidal gold 198Au

    International Nuclear Information System (INIS)

    Cammarosano, S.A.

    1979-01-01

    The preparation with simple equipment of radioactive colloidal gold of particle size about approximately 300 A from seed colloid stabilized by gelatine is described. Some physico-chemical parameters which can affect the process of formation of these colloidal particles are analysed; particle size has been meassured with an electron microscope. The colloid stability has been studied as a function of dilution, age and pH. Nucleation and growth of radioactive colloidal gold have been studied using spectrophotometry. Absorption spectra of the two ones are presented and compared. Quality control of the production process is verified through measurement of parameters, such as radioactive and radiochemical purity and biological distribution in laboratorial animals. This distribution was evalusted for rats injected endovenously with the gold colloidal solution.(Author) [pt

  14. Electrical properties of fast ion conducting silver based borate glasses: Application in solid battery

    International Nuclear Information System (INIS)

    Masoud, Emad M.; Khairy, M.; Mousa, M.A.

    2013-01-01

    Graphical abstract: -- Highlights: •AgI dopant created more opened borate network structure. •Dielectric constant and loss values increased with AgI concentration. •AgI dopant enhanced both ion migration and orientation. •0.6 AgI–0.27 Ag 2 O–0.13 B 2 O 3 showed the highest DC-conductivity at room temperature. •It showed also good life time as a solid electrolyte in solid battery at room temperature. -- Abstract: The electrical properties of the ternary ionic conducting glass system xAgI–(1 – x)[0.67Ag 2 O–0.33B 2 O 3 ], where x = 0.4 , 0.5, 0.6, 0.7 and 0.8, were studied for emphasizing the influence of silver iodide concentration on the transport properties in the based borate glasses. The glasses were prepared by melt quenching technique and characterized using X-ray diffraction (XRD), FT-IR spectra and differential thermal analysis (DTA). XRD confirmed a glassy nature for all investigated compositions. Electrical conductivity (σ), dielectric constant (ε′), dielectric loss (ε ″ ) and impedance spectra (Z′–Z′′) were studied for all samples at a frequency range of 0–10 6 Hz and over a temperature range of 303–413 K. Changes of conductivity and dielectric properties with composition, temperature and frequency were analyzed and discussed. A silver iodine battery using glassy electrolyte sample with the highest ionic conductivity (x = 0.6) was studied

  15. Electrically conductive borate-based bioactive glass scaffolds for bone tissue engineering applications.

    Science.gov (United States)

    Turk, Mert; Deliormanlı, Aylin M

    2017-07-01

    In this study, electrically conductive, borate-based, porous 13-93B3 bioactive glass composite scaffolds were prepared using a polymer foam replication technique. For this purpose, a slurry containing 40 vol% glass particles and 0-10 wt% graphene nanoplatelets was prepared by dispersing the particles in ethanol in the presence of ethyl cellulose. Composite scaffolds were subjected to a controlled heat treatment, in air atmosphere, to decompose the foam and sinter the glass particles into a dense network. It was found that the applied heat treatment did not influence the structure of graphene in the glass network. Graphene additions did not negatively affect the mechanical properties and enhanced the electrical conductivity of the glass scaffolds. In X-ray diffraction analysis, the crystalline peak corresponding to hydroxyapatite was observed in all the samples suggesting that all of the samples were bioactive after 30 days of immersion in simulated body fluid. However, Fourier transform infrared spectroscopy analysis and scanning electron microscope observations revealed that hydroxyapatite formation rate decreased with increasing graphene concentration especially for samples treated in simulated body fluid for shorter times. Based on the cytotoxicity assay findings, the MC3T3-E1 cell growth was significantly inhibited by the scaffolds containing higher amount of graphene compared to bare glass scaffolds. Best performance was obtained for 5 wt% graphene which yielded an enhancement of electrical conductivity with moderate cellular response and in vitro hydroxyapatite forming ability. The study revealed that the electrically conductive 13-93B3 graphene scaffolds are promising candidates for bone tissue engineering applications.

  16. High-Performance Electrochemical Catalysts Based on Three-Dimensional Porous Architecture with Conductive Interconnected Networks.

    Science.gov (United States)

    Wang, Dong; Wang, Jie; Liu, Zi-En; Yang, Xiangdong; Hu, Xiaoxia; Deng, Jinqi; Yang, Nianjun; Wan, Qijin; Yuan, Quan

    2016-10-26

    The electrochemical applications of traditional carbon nanomaterials such as carbon nanotubes (CNTs) and graphene (G) powders are significantly impeded by their poor three-dimensional (3D) conductivity and lack of hierarchical porous structure. Here, we have constructed a 3D highly conductive CNTs networks and further combined it with mesoporous carbon (mC) for the creation of a core-shell structured (CNT@mC) composite sponge that featured 3D conductivity and hierarchical porous structure. In the composite sponge, interconnected CNTs efficiently eliminates the contact resistance and the hierarchical pores significantly facilitate the mass transport. The electron transfer rates, electroactive surface area and catalytic activity of the CNT@mC composite sponge based catalysts were tested in the direct methanol fuel cells (DMFCs) and electrochemical sensors. In DMFCs, the Pd nanoparticles deposited CNT@mC showed significantly improved catalytic activity and methanol oxidization current. As for amperometric sensing of endocrine disrupting compounds (EDCs), CNT@mC-based catalyst gave a liner range from 10 nM to 1 mM for bisphenol A (BPA) detection and showed great promise for simultaneous detection of multiple EDCs. BPA recovery from environmental water further indicated the potential practical applications of the sensor for BPA detection. Finally, the electrochemical performance of CNT@mC were also investigated in impedimetric sensors. Good selectivity was obtained in impedimetric sensing of BPA and the detection limit was measured to be 0.3 nM. This study highlighted the exceptional electrochemical properties of the CNT@mC composite sponge enabled by its 3D conductivity and hierarchical porous structure. The strategy described may further pave a way for the creation of novel functional materials through integrating multiple superior properties into a single nanostructure for future clean energy technologies and environmental monitoring systems.

  17. Does colloid shape affect detachment of colloids by a moving air-water interface?

    Science.gov (United States)

    Aramrak, Surachet; Flury, Markus; Harsh, James B; Zollars, Richard L; Davis, Howard P

    2013-05-14

    Air-water interfaces interact strongly with colloidal particles by capillary forces. The magnitude of the interaction force depends on, among other things, the particle shape. Here, we investigate the effects of particle shape on colloid detachment by a moving air-water interface. We used hydrophilic polystyrene colloids with four different shapes (spheres, barrels, rods, and oblong disks), but otherwise identical surface properties. The nonspherical shapes were created by stretching spherical microspheres on a film of polyvinyl alcohol (PVA). The colloids were then deposited onto the inner surface of a glass channel. An air bubble was introduced into the channel and passed through, thereby generating a receding followed by an advancing air-water interface. The detachment of colloids by the air-water interfaces was visualized with a confocal microscope, quantified by image analysis, and analyzed statistically to determine significant differences. For all colloid shapes, the advancing air-water interface caused pronounced colloid detachment (>63%), whereas the receding interface was ineffective in colloid detachment (colloid shapes, the barrels were most readily removed (94%) by the advancing interface, followed by the spheres and oblong disks (80%) and the rods (63%). Colloid detachment was significantly affected by colloid shape. The presence of an edge, as it occurs in a barrel-shaped colloid, promoted colloid detachment because the air-water interface is being pinned at the edge of the colloid. This suggests that the magnitude of colloid mobilization and transport in porous media is underestimated for edged particles and overestimated for rodlike particles when a sphere is used as a model colloid.

  18. A novel colloidal gold-based lateral flow immunoassay for rapid simultaneous detection of cyromazine and melamine in foods of animal origin.

    Science.gov (United States)

    Le, Tao; Yan, Peifeng; Xu, Jian; Hao, Youjing

    2013-06-01

    A rapid and sensitive lateral flow immunoassay (LFIA) based on competitive format was developed and validated for simultaneous detection of cyromazine (CA) and melamine (MA) in foods of animal origin. With this method, the cut-off value for the two test lines were achieved at 25 ng/g, which was lower than the maximum residue levels (MRLs) established for CA and MA. At three fortified levels (50, 100, and 150 ng/g), the recoveries for CA and MA ranged from 73.9% to 104.2% with the relative standard deviation (RSD) less than 11.9%, based on within day and interday analysis. The lower detection limit for CA and MA in matrix sample were 0.22 ng/ml and 0.26 ng/ml, respectively, which were lower than those of published literatures. A parallel analysis of CA and MA in real samples conducted by HPLC showed comparable results to those obtained from LFIA. The results of LFIA were in good agreement with those of high performance liquid chromatography (HPLC) in the analysis of CA and MA in foods of animal origin, demonstrating the practical applicability of the developed assay in real samples. Overall, to our knowledge, this is the first report of quantitative or semi-quantitative simultaneous detection for CA and MA by immunochromatographic assay. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Efficient digital implementation of a conductance-based globus pallidus neuron and the dynamics analysis

    Science.gov (United States)

    Yang, Shuangming; Wei, Xile; Deng, Bin; Liu, Chen; Li, Huiyan; Wang, Jiang

    2018-03-01

    Balance between biological plausibility of dynamical activities and computational efficiency is one of challenging problems in computational neuroscience and neural system engineering. This paper proposes a set of efficient methods for the hardware realization of the conductance-based neuron model with relevant dynamics, targeting reproducing the biological behaviors with low-cost implementation on digital programmable platform, which can be applied in wide range of conductance-based neuron models. Modified GP neuron models for efficient hardware implementation are presented to reproduce reliable pallidal dynamics, which decode the information of basal ganglia and regulate the movement disorder related voluntary activities. Implementation results on a field-programmable gate array (FPGA) demonstrate that the proposed techniques and models can reduce the resource cost significantly and reproduce the biological dynamics accurately. Besides, the biological behaviors with weak network coupling are explored on the proposed platform, and theoretical analysis is also made for the investigation of biological characteristics of the structured pallidal oscillator and network. The implementation techniques provide an essential step towards the large-scale neural network to explore the dynamical mechanisms in real time. Furthermore, the proposed methodology enables the FPGA-based system a powerful platform for the investigation on neurodegenerative diseases and real-time control of bio-inspired neuro-robotics.

  20. Quantifying rainfall-derived inflow and infiltration in sanitary sewer systems based on conductivity monitoring

    Science.gov (United States)

    Zhang, Mingkai; Liu, Yanchen; Cheng, Xun; Zhu, David Z.; Shi, Hanchang; Yuan, Zhiguo

    2018-03-01

    Quantifying rainfall-derived inflow and infiltration (RDII) in a sanitary sewer is difficult when RDII and overflow occur simultaneously. This study proposes a novel conductivity-based method for estimating RDII. The method separately decomposes rainfall-derived inflow (RDI) and rainfall-induced infiltration (RII) on the basis of conductivity data. Fast Fourier transform was adopted to analyze variations in the flow and water quality during dry weather. Nonlinear curve fitting based on the least squares algorithm was used to optimize parameters in the proposed RDII model. The method was successfully applied to real-life case studies, in which inflow and infiltration were successfully estimated for three typical rainfall events with total rainfall volumes of 6.25 mm (light), 28.15 mm (medium), and 178 mm (heavy). Uncertainties of model parameters were estimated using the generalized likelihood uncertainty estimation (GLUE) method and were found to be acceptable. Compared with traditional flow-based methods, the proposed approach exhibits distinct advantages in estimating RDII and overflow, particularly when the two processes happen simultaneously.

  1. An Exact Method to Determine the Conductivity of Aqueous Solutions in Acid-Base Titrations

    Directory of Open Access Journals (Sweden)

    Norma Rodríguez-Laguna

    2015-01-01

    Full Text Available Several works in the literature show that it is possible to establish the analytic equations to estimate the volume V of a strong base or a strong acid (Vb and Va, resp. being added to a solution of a substance or a mix of substances during an acid-base titration, as well as the equations to estimate the first derivative of the titration plot dpH/dV, and algebraic expressions to determine the buffer β capacity with dilution βdil. This treatment allows establishing the conditions of thermodynamic equilibria for all species within a system containing a mix of species from one or from various polyacid systems. The present work shows that it is possible to determine exactly the electric conductivity of aqueous solutions for these Brønsted acid-base titrations, because the functional relation between this property and the composition of the system in equilibrium is well known; this is achieved using the equivalent conductivity λi values of each of the ions present in a given system. The model employed for the present work confirms the experimental outcomes with the H2SO4, B(OH3, CH3COOH, and H3PO4 aqueous solutions’ titration.

  2. Inorganic proton conducting electrolyte coupled oxide-based dendritic transistors for synaptic electronics.

    Science.gov (United States)

    Wan, Chang Jin; Zhu, Li Qiang; Zhou, Ju Mei; Shi, Yi; Wan, Qing

    2014-05-07

    Ionic/electronic hybrid devices with synaptic functions are considered to be the essential building blocks for neuromorphic systems and brain-inspired computing. Here, artificial synapses based on indium-zinc-oxide (IZO) transistors gated by nanogranular SiO2 proton-conducting electrolyte films are fabricated on glass substrates. Spike-timing dependent plasticity and paired-pulse facilitation are successfully mimicked in an individual bottom-gate transistor. Most importantly, dynamic logic and dendritic integration established by spatiotemporally correlated spikes are also mimicked in dendritic transistors with two in-plane gates as the presynaptic input terminals.

  3. Design and Fabrication of Graphene Reinforced Polymer Conductive Patch-Based Inset Fed Microstrip Antenna

    Science.gov (United States)

    Deepak, A.; Kannan, P. Muthu; Shankar, P.

    This work explores the design and fabrication of graphene reinforced polyvinylidene fluoride (PVDF) patch-based microstrip antenna. Primarily, antenna was designed at 6GHz frequency and simulation results were obtained using Ansoft HFSS tool. Later fabrication of antenna was carried out with graphene-PVDF films as conducting patch deposited on bakelite substrate and copper as ground plane. Graphene-PVDF films were prepared using solvent casting process. The radiation efficiency of fabricated microstrip patch antenna was 48% entailing it to be adapted as a practically functional antenna. Both simulated and the practical results were compared and analyzed.

  4. Use of high-thermal conductive aluminum nitride based ceramics in vacuum UHF electronic devices

    Directory of Open Access Journals (Sweden)

    Chasnyk V. I.

    2013-06-01

    Full Text Available Analysis of properties and characteristics of the alumina, beryllium oxide and aluminum nitride based ceramic materials used in UHF electronic devices has been made. It was shown that the complex of parameters including structural and functional characteristics of the high-thermal conductive aluminum nitride ceramics prevail over all types of alumina ceramics and is not lower than the same characteristics of the beryllium oxide ceramics especially at the temperatures higher than 450 °C. The examples of the prevailing use of the aluminum nitride ceramics inside vacuum UHF-region devices: TWT’s and klystrons.

  5. Team-based learning instruction for responsible conduct of research positively impacts ethical decision-making.

    Science.gov (United States)

    McCormack, Wayne T; Garvan, Cynthia W

    2014-01-01

    Common practices for responsible conduct of research (RCR) instruction have recently been shown to have no positive impact on and possibly to undermine ethical decision-making (EDM). We show that a team-based learning (TBL) RCR curriculum results in some gains in decision ethicality, the use of more helpful metacognitive reasoning strategies in decision-making, and elimination of most negative effects of other forms of RCR instruction on social-behavioral responses. TBL supports the reasoning strategies and social mechanisms that underlie EDM and ethics instruction, and may provide a more effective method for RCR instruction than lectures and small group discussion.

  6. Colloid Titration--A Rapid Method for the Determination of Charged Colloid.

    Science.gov (United States)

    Ueno, Keihei; Kina, Ken'yu

    1985-01-01

    "Colloid titration" is a volumetric method for determining charged polyelectrolytes in aqueous solutions. The principle of colloid titration, reagents used in the procedure, methods of endpoint detection, preparation of reagent solutions, general procedure used, results obtained, and pH profile of colloid titration are considered. (JN)

  7. Colloidal paradigm in supercapattery electrode systems

    Science.gov (United States)

    Chen, Kunfeng; Xue, Dongfeng

    2018-01-01

    Among decades of development, electrochemical energy storage systems are now sorely in need of a new design paradigm at the nano size and ion level to satisfy the higher energy and power demands. In this review paper, we introduce a new colloidal electrode paradigm for supercapattery that integrates multiple-scale forms of matter, i.e. ion clusters, colloidal ions, and nanosized materials, into one colloid system, coupled with multiple interactions, i.e. electrostatic, van der Waals forces, and chemical bonding, thus leading to the formation of many redox reactive centers. This colloidal electrode not only keeps the original ionic nature in colloidal materials, but also creates a new attribute of high electroactivity. Colloidal supercapattery is a perfect application example of the novel colloidal electrode, leading to higher specific capacitance than traditional electrode materials. The high electroactivity of the colloidal electrode mainly comes from the contribution of exposed reactive centers, owing to the confinement effect of carbon and a binder matrix. Systematic and thorough research on the colloidal system will significantly promote the development of fundamental science and the progress of advanced energy storage technology.

  8. Intrinsic and Carrier Colloid-facilitated transport of lanthanides through discrete fractures in chalk

    Science.gov (United States)

    Weisbrod, N.; Tran, E. L.; Klein-BenDavid, O.; Teutsch, N.

    2015-12-01

    Geological disposal of high-level radioactive waste is the long term solution for the disposal of long lived radionuclides and spent fuel. However, some radionuclides might be released from these repositories into the subsurface as a result of leakage, which ultimately make their way into groundwater. Engineered bentonite barriers around nuclear waste repositories are generally considered sufficient to impede the transport of radionuclides from their source to the groundwater. However, colloidal-sized mobile bentonite particles ("carrier" colloids) originating from these barriers have come under investigation as a potential transport vector for radionuclides sorbed to them. As lanthanides are generally accepted to have the same chemical behaviors as their more toxic actinide counterparts, lanthanides are considered an acceptable substitute for research on radionuclide transportation. This study aims to evaluate the transport behaviors of lanthanides in colloid-facilitated transport through a fractured chalk matrix and under geochemical conditions representative the Negev desert, Israel. The migration of Ce both with and without colloidal particles was explored and compared to the migration of a conservative tracer (bromide) using a flow system constructed around a naturally fractured chalk core. Results suggest that mobility of Ce as a solute is negligible. In experiments conducted without bentonite colloids, the 1% of the Ce that was recovered migrated as "intrinsic" colloids in the form of carbonate precipitates. However, the total recovery of the Ce increased to 9% when it was injected into the core in the presence of bentonite colloids and 13% when both bentonite and precipitate colloids were injected. This indicates that lanthanides are essentially immobile in chalk as a solute but may be mobile as carbonate precipitates. Bentonite colloids, however, markedly increase the mobility of lanthanides through fractured chalk matrices.

  9. Release of colloids and polycyclic aromatic hydrocarbons from a contaminated soil under natural conditions

    Science.gov (United States)

    Jann, S.; Totsche, K. U.; Kögel-Knabner, I.

    2003-04-01

    Mobile colloidal particles play an important role in the carrier-facilitated transport of strongly sorbing solutes. They act as a possible sorbent for contaminants and are possible pollutant carriers. Knowledge on the release and transport of soil-borne colloidal particles is mandatory for the understanding of the mobility of hydrophobic or surface-complexing contaminants. In soils, the major fraction of colloidal phase particles is of organic provenience. Their mobility in soils is controlled by the release from and the interactions with the immobile solid phase, by microbial formation processes as well as by the flow regime. Important factors of the release and transport are the site-specific meteorological conditions like groundwater recharge, temperature and moisture regime, and amount and distribution of precipitation. We studied the release of natural organic colloids and polycyclic aromatic hydrocarbons (PAH) from a coarse textured, calcareous porous media under field conditions. Three natural gradient lysimeters and nine precipitation gauges were installed at a contaminated site. Sampling of the seepage water was triggered by rainfall events. Analysis of the samples comprised the determination of the 16 EPA-PAH in the liquid phase and in the colloidal and suspended particle fraction, dissolved and colloidal phase organic carbon (DCOC), pH, electrolytic conductivity and turbidity. Preliminary results show a direct response of the release of colloids to strong rainfall events. The amount of seepage corresponds directly with the precipitation rate. Mean concentrations of DCOC in the seepage water range between 2 and 6 mg/l. PAH concentrations are very low in the liquid phase but reach up to 660 mg/kg in the colloidal and suspended particle fraction. This points to the importance of colloid-facilitated transport of the contaminant through the unsaturated soil zone.

  10. Colloidal quantum dot photodetectors

    KAUST Repository

    Konstantatos, Gerasimos

    2011-05-01

    We review recent progress in light sensors based on solution-processed materials. Spin-coated semiconductors can readily be integrated with many substrates including as a post-process atop CMOS silicon and flexible electronics. We focus in particular on visible-, near-infrared, and short-wavelength infrared photodetectors based on size-effect-tuned semiconductor nanoparticles made using quantum-confined PbS, PbSe, Bi 2S3, and In2S3. These devices have in recent years achieved room-temperature D values above 1013 Jones, while fully-depleted photodiodes based on these same materials have achieved MHz response combined with 1012 Jones sensitivities. We discuss the nanoparticle synthesis, the materials processing, integrability, temperature stability, physical operation, and applied performance of this class of devices. © 2010 Elsevier Ltd. All rights reserved.

  11. Concept for a MEMS-type vacuum sensor based on electrical conductivity measurements

    Directory of Open Access Journals (Sweden)

    F. J. Giebel

    2017-11-01

    Full Text Available The concept of the micro-structured vacuum sensor presented in this article is the measurement of the electrical conductivity of thinned gases in order to develop a small, economical and quite a simple type of vacuum sensor. There are already some approaches for small vacuum sensors. Most of them are based on conservative measurement principles similar to those used in macroscopic vacuum gauges. Ionization gauges use additional sources of energy, like hot cathodes, ultraviolet radiation or high voltage for example, for ionizing gas molecules and thereby increasing the number of charge carriers for measuring low pressures. In contrast, the concept discussed here cannot be found in macroscopic sensor systems because it depends on the microscopic dimension of a gas volume defined by two electrodes. Here we present the concept and the production of a micro-structured vacuum sensor chip, followed by the electrical characterization. Reference measurements with electrodes at a distance of about 1 mm showed currents in the size of picoampere and a conductivity depending on ambient pressure. In comparison with these preliminary measurements, fundamental differences regarding pressure dependence of the conductivity are monitored in the electrical characterization of the micro-structured sensor chip. Finally the future perspectives of this sensor concept are discussed.

  12. Large-scale assembly of colloidal particles

    Science.gov (United States)

    Yang, Hongta

    increase of the effective refractive index of the diffractive medium, resulting in the red-shift of the optical stop bands. The wavelength shift is linearly proportional to the vapor partial pressure for a spectrum of vapors. Optical simulation and theoretical prediction based on Kelvin equation suggest that a liquid film is formed on the walls of the macropores during vapor condensation. The third topic describes introducing doctor blade coating fabricated large area and low cost macroporous films for thermochromic smart windows, which are useful for energy control in glazed buildings. The fabricated macroporous polymer films exhibit brilliant colors and are capable of reflecting solar radiation when in-situ heated, and become transparent as cavities are filled with a solvent which has the same refractive index as that of the polymer when cooled to building temperature. The fourth topic reports the roll-to roll fabricated excellent water-repelling and self-cleaning macroporous polymer films. The size of the voids can be easily controlled by tuning the duration of an oxygen reactive-ion etching process prior to the removal of the templating silica spheres from silica colloidal-polymer composites. After surface functionalization with fluorosilane, superhydrophobic surface with large apparent water contact angle and small sliding angle can be obtained. The self-cleaning functionality can be achieved on superhydrophobic macroporous coatings by preventing bacterial contamination is further demonstrated. The fifth topic presented is that the template macroporous polymer films with interconnected voids and uniform interconnecting nanopores can be directly used as filtration membranes to achieve size-exclusive separation of particles. The results also demonstrate that more than 85% of small sized particles are recovered after filtration. The results also demonstrate that Escherichia coli can be filtrated by the from macroporous polymer films aqueous solution.

  13. Convergence of Cell Based Finite Volume Discretizations for Problems of Control in the Conduction Coefficients

    DEFF Research Database (Denmark)

    Evgrafov, Anton; Gregersen, Misha Marie; Sørensen, Mads Peter

    2011-01-01

    We present a convergence analysis of a cell-based finite volume (FV) discretization scheme applied to a problem of control in the coefficients of a generalized Laplace equation modelling, for example, a steady state heat conduction. Such problems arise in applications dealing with geometric optimal......, whereas the convergence of the coefficients happens only with respect to the "volumetric" Lebesgue measure. Additionally, depending on whether the stationarity conditions are stated for the discretized or the original continuous problem, two distinct concepts of stationarity at a discrete level arise. We...... provide characterizations of limit points, with respect to FV mesh size, of globally optimal solutions and two types of stationary points to the discretized problems. We illustrate the practical behaviour of our cell-based FV discretization algorithm on a numerical example....

  14. Gold nanorod-incorporated gelatin-based conductive hydrogels for engineering cardiac tissue constructs.

    Science.gov (United States)

    Navaei, Ali; Saini, Harpinder; Christenson, Wayne; Sullivan, Ryan Tanner; Ros, Robert; Nikkhah, Mehdi

    2016-09-01

    The development of advanced biomaterials is a crucial step to enhance the efficacy of tissue engineering strategies for treatment of myocardial infarction. Specific characteristics of biomaterials including electrical conductivity, mechanical robustness and structural integrity need to be further enhanced to promote the functionalities of cardiac cells. In this work, we fabricated UV-crosslinkable gold nanorod (GNR)-incorporated gelatin methacrylate (GelMA) hybrid hydrogels with enhanced material and biological properties for cardiac tissue engineering. Embedded GNRs promoted electrical conductivity and mechanical stiffness of the hydrogel matrix. Cardiomyocytes seeded on GelMA-GNR hybrid hydrogels exhibited excellent cell retention, viability, and metabolic activity. The increased cell adhesion resulted in abundance of locally organized F-actin fibers, leading to the formation of an integrated tissue layer on the GNR-embedded hydrogels. Immunostained images of integrin β-1 confirmed improved cell-matrix interaction on the hybrid hydrogels. Notably, homogeneous distribution of cardiac specific markers (sarcomeric α-actinin and connexin 43), were observed on GelMA-GNR hydrogels as a function of GNRs concentration. Furthermore, the GelMA-GNR hybrids supported synchronous tissue-level beating of cardiomyocytes. Similar observations were also noted by, calcium transient assay that demonstrated the rhythmic contraction of the cardiomyocytes on GelMA-GNR hydrogels as compared to pure GelMA. Thus, the findings of this study clearly demonstrated that functional cardiac patches with superior electrical and mechanical properties can be developed using nanoengineered GelMA-GNR hybrid hydrogels. In this work, we developed gold nanorod (GNR) incorporated gelatin-based hydrogels with suitable electrical conductivity and mechanical stiffness for engineering functional cardiac tissue constructs (e.g. cardiac patches). The synthesized conductive hybrid hydrogels properly

  15. Conductive hearing loss in four dogs associated with the use of ointment-based otic medications.

    Science.gov (United States)

    Cole, Lynette K; Rajala-Schultz, Päivi J; Lorch, Gwendolen

    2018-04-17

    Hearing loss (HL) is classified as conductive when sound transmission is compromised in the ear canal or middle ear, or sensorineural when there is an abnormality of the receptor cells of the cochlea or auditory pathway. Hearing in dogs is evaluated using the brainstem auditory evoked response (BAER) test. Our objective was to characterize BAER findings pre- and post-ear flushing in four dogs with acute HL following application of an ointment-based otic medication containing betamethasone, clotrimazole and gentamicin in a mineral oil-based system containing a plasticized hydrocarbon gel. Dogs, ranging from 9 to 11 years old, that had been treated with the otic medication for one to three weeks prior to hearing loss and on otoscopic examination had evidence of medication in the horizontal ear canals. Dogs were anaesthetized for an ear flush to remove the medication from the ear canals. Hearing was assessed using BAER testing, measurements were initiated with 116 decibel peak equivalent sound pressure level (dBpeSPL) click. Estimated threshold was defined as the lowest intensity in dB in which wave V was still present. Post-ear flush the estimated threshold improved in both ears of all dogs (mean 22.3 dB; range 13-41 dB), confirming conductive HL due to the otic medication. All owners noted an improvement in their dog's hearing post-ear flush, validating the BAER findings. These results emphasize the importance of an ear flush to remove otic medications in dogs that experience acute HL, to determine if the HL is conductive, and if so, to restore hearing. © 2018 ESVD and ACVD.

  16. Synthesis, characterization, biological and electrical conductivity studies of some Schiff base metal complexes

    Directory of Open Access Journals (Sweden)

    A. R. Yaul

    2014-05-01

    Full Text Available Metal complexes of VO(IV, Zr(IV, Th(IV and UO2(VI with Schiff base ligands derived from 4-nitrobenzoylhydrazide with 2-hydroxy-5-methylacetophenone (H2L1 or 2-hydroxy-5-chloroacetophenone (H2L2 have been prepared. All the complexes have been characterized on the basis of elemental analyses, magnetic susceptibility measurement, electronic and IR spectra and thermogravimetric analysis. The IR spectral data suggested that the ligands behave as dibasic tridentate moiety towards the central metal ion coordinating through phenolic oxygen, enolic oxygen and azomethine nitrogen atoms. The elemental analyses show a 1:1 metal:ligand stoichiometry for all the complexes except Th(IV which has 1:2 stoichiometry. The thermal analysis evidenced that thermal transformations of complexes are processes according to TG curves including dehydration, thermolysis and oxidative degradation of Schiff base. The final product of decomposition is the most stable metallic oxide. The kinetic analysis of the thermogravimetric data was performed by using the Coats-Redfern method. Solid state electrical conductivity of the complexes has been measured in their compressed pellet form over a 310-413 K temperature range. All the complexes show semiconducting behavior as their conductivity increases with increasing temperature and a function of ionic size. All the complexes along with ligands were also screened for their antibacterial and antifungal activities. DOI: http://dx.doi.org/10.4314/bcse.v28i2.9

  17. Investigation of a Biocompatible Polyurethane-Based Isotropically Conductive Adhesive for UHF RFID Tag Antennas

    Science.gov (United States)

    Yang, Cheng; Yuen, Matthew M. F.; Gao, Bo; Ma, Yuhui; Wong, C. P.

    2011-01-01

    As a candidate dispersant for silver-based isotropically conductive adhesives (ICAs), polyurethane (PU) is an environmentally benign material that can withstand a high deformation rate and that exhibits excellent reliability. In this work we investigated methyl ethyl ketoxime (MEKO) blocked isophorone diisocyanate (IPDI) and MEKO blocked hexamethylene diisocyanate (HDI) as dispersant materials, and we characterize the electrical conductivity, mechanical properties, and reliability of these PU-based ICAs with silver-flake filler content ranging from 30 wt.% to 75 wt.%. Results of temperature-humidity testing (THT) at 85°C and 85% relative humidity (RH) and thermal cycling testing (TCT) at -40°C to 125°C show that these ICAs have excellent reliability. Our experimental results suggest that the MEKO blocked PU dispersants are suitable for preparing ultralow-cost, flexible, high-performance ICAs for printing antennas for ultrahigh-frequency radiofrequency identification (RFID) tags. These tags can potentially be used for identifying washable items and food packaging.

  18. Evaluation of Tap Water Based on Sensor Array and Conducting Nanostructured Polymers

    Directory of Open Access Journals (Sweden)

    Eduarda Carvalho

    2016-11-01

    Full Text Available A sensor system, adapted to evaluate tap water, was fabricated and tested. Interdigitated  gold-coated microelectrodes were covered with various conducting polymers, single or mixed, under several different conditions. Polymer films were laid down by a  self-assembly technique and their impedance was analyzed over a range of frequencies from 1Hz to 1MHz. Samples collected from different localities at São Paulo state (Brazil were used. The results of sensorial system analyzed by Principal Component Analysis had allowed completing discrimination of tap water samples. Good discrimination between the sensors was observed when there was obtained a PCA with different samples, obtaining the total variance (PC1 = 62.03%; PC2 = 37.97% of the observations. The sensorial system based in global selectivity using interdigitated electrode and nanostruturated conducting polymers allowed a statistical discrimination of sample waters of different locations. The future expectations are the upgrading of the system and implementation of a monitoring of tap water systems based nanostructured sensors.

  19. New anthracene-based-phtalocyanine semi-conducting materials: Synthesis and optoelectronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Kahouech, M.S. [Laboratoire de Chimie Organique et Analytique, Institut Supérieur de l' Education et de la Formation Continue (Université El Manar), Bardo 2000 (Tunisia); Hriz, K., E-mail: khaledhriz@gmail.com [Laboratoire des Interfaces et Matériaux Avancés (LIMA), Faculté des Sciences de Monastir (Université de Monastir), Bd. de l' Environnement, Monastir 5019 (Tunisia); Touaiti, S.; Bassem, J. [Laboratoire de Chimie Organique et Analytique, Institut Supérieur de l' Education et de la Formation Continue (Université El Manar), Bardo 2000 (Tunisia)

    2016-03-15

    Highlights: • Synthesis of tow phtalocyanines based on the anthracene and tetrazole. • Semi-conducting supramolecular material. • Good PL quantum yield. • The film morphology of the phtalocynine containing tetrazole group enhanced the carrier mobility. - Abstract: A new anthracene-based semi-conducting phtalocyanines AnPc and AnPc-Tr were synthesized in solvent-free conditions. The supramolecular structure of these compounds was confirmed by NMR and FT-IR spectroscopies. Their optical properties were investigated by UV–vis and photoluminescence spectroscopies. The optical gaps were estimated from the absorption-onsets films, and the obtained values were of 1.50 eV and 1.47 eV for AnPc-Tr and AnPc respectively. In solid state, a weaker π–π-interactions of conjugated systems were obtained in the case of AnPc-Tr in comparison with AnPc. This behavior was explained by steric hindrance of triazol groups, which decrease the planarity of macromolecular structure. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis; two phtalocyanine derivatives show a comparable ionization potential. The phtalacyanine containing triazole groups (AnPc-Tr) reveals a higher electron affinity in comparison with AnPc. Single-layer diode devices were fabricated and showed relatively low turn-on voltages.

  20. Bacteriostatic Substrate by Conductivity Method and Electric Spark Discharge Method Combined with Electrospinning for Silver Dressing

    Directory of Open Access Journals (Sweden)

    Kuo-Hsiung Tseng

    2016-01-01

    Full Text Available This study uses the conductivity method, Electric Spark Discharge Method, and the electrospinning technique to develop a better silver-based antibacterial agent. The preparation process is free of chemical substances and also conforms to the green energy-saving process. The silver iodide was prepared in an iodine agar medium by using the conductivity method. Multiple bacteriostasis experiments showed that the molds grew in the position with iodine of the culture medium after 6 days, as well as in the position with silver iodide after 10 days. The results prove that silver iodide has better bacteriostatic ability than povidone iodine. The nanosilver colloid was prepared in the PVA solution by using the Electric Spark Discharge Method. UV-Vis, Zetasizer, and SEM-EDX analyses proved that the PVA solution contained nanosilver colloid with good suspension stability. Finally, the electrospinning technique was used to spin the PVA solution with nanosilver colloid into the PVA nanofibrous membrane. According to UV-Vis analysis, the absorption peak of this nanofibrous membrane is about 415 nm, meaning this nanofibrous membrane contains nucleate nanosilver colloid, and is very suitable for antiseptic dressing.